mirror of https://github.com/python/cpython
bpo-41972: Tweak fastsearch.h string search algorithms (GH-27091)
This commit is contained in:
Dennis Sweeney
GitHub
parent
b2cf2513f9
commit
d01dceb88b
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@ -0,0 +1 @@
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Tuned the string-searching algorithm of fastsearch.h to have a shorter inner loop for most cases.
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@ -170,10 +170,16 @@ STRINGLIB(rfind_char)(const STRINGLIB_CHAR* s, Py_ssize_t n, STRINGLIB_CHAR ch)
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/* Change to a 1 to see logging comments walk through the algorithm. */
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#if 0 && STRINGLIB_SIZEOF_CHAR == 1
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# define LOG(...) printf(__VA_ARGS__)
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# define LOG_STRING(s, n) printf("\"%.*s\"", n, s)
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# define LOG_STRING(s, n) printf("\"%.*s\"", (int)(n), s)
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# define LOG_LINEUP() do { \
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LOG("> "); LOG_STRING(haystack, len_haystack); LOG("\n> "); \
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LOG("%*s",(int)(window_last - haystack + 1 - len_needle), ""); \
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LOG_STRING(needle, len_needle); LOG("\n"); \
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} while(0)
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#else
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# define LOG(...)
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# define LOG_STRING(s, n)
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# define LOG_LINEUP()
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#endif
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Py_LOCAL_INLINE(Py_ssize_t)
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@ -287,11 +293,11 @@ STRINGLIB(_factorize)(const STRINGLIB_CHAR *needle,
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return cut;
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}
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#define SHIFT_TYPE uint8_t
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#define NOT_FOUND ((1U<<(8*sizeof(SHIFT_TYPE))) - 1U)
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#define SHIFT_OVERFLOW (NOT_FOUND - 1U)
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#define TABLE_SIZE_BITS 6
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#define SHIFT_TYPE uint8_t
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#define MAX_SHIFT UINT8_MAX
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#define TABLE_SIZE_BITS 6u
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#define TABLE_SIZE (1U << TABLE_SIZE_BITS)
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#define TABLE_MASK (TABLE_SIZE - 1U)
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@ -300,12 +306,13 @@ typedef struct STRINGLIB(_pre) {
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Py_ssize_t len_needle;
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Py_ssize_t cut;
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Py_ssize_t period;
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Py_ssize_t gap;
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int is_periodic;
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SHIFT_TYPE table[TABLE_SIZE];
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} STRINGLIB(prework);
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Py_LOCAL_INLINE(void)
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static void
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STRINGLIB(_preprocess)(const STRINGLIB_CHAR *needle, Py_ssize_t len_needle,
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STRINGLIB(prework) *p)
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{
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@ -319,145 +326,156 @@ STRINGLIB(_preprocess)(const STRINGLIB_CHAR *needle, Py_ssize_t len_needle,
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if (p->is_periodic) {
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assert(p->cut <= len_needle/2);
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assert(p->cut < p->period);
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p->gap = 0; // unused
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}
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else {
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// A lower bound on the period
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p->period = Py_MAX(p->cut, len_needle - p->cut) + 1;
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}
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// Now fill up a table
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memset(&(p->table[0]), 0xff, TABLE_SIZE*sizeof(SHIFT_TYPE));
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assert(p->table[0] == NOT_FOUND);
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assert(p->table[TABLE_MASK] == NOT_FOUND);
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for (Py_ssize_t i = 0; i < len_needle; i++) {
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Py_ssize_t shift = len_needle - i;
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if (shift > SHIFT_OVERFLOW) {
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shift = SHIFT_OVERFLOW;
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// The gap between the last character and the previous
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// occurrence of an equivalent character (modulo TABLE_SIZE)
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p->gap = len_needle;
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STRINGLIB_CHAR last = needle[len_needle - 1] & TABLE_MASK;
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for (Py_ssize_t i = len_needle - 2; i >= 0; i--) {
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STRINGLIB_CHAR x = needle[i] & TABLE_MASK;
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if (x == last) {
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p->gap = len_needle - 1 - i;
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break;
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}
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}
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p->table[needle[i] & TABLE_MASK] = Py_SAFE_DOWNCAST(shift,
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Py_ssize_t,
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SHIFT_TYPE);
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}
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// Fill up a compressed Boyer-Moore "Bad Character" table
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Py_ssize_t not_found_shift = Py_MIN(len_needle, MAX_SHIFT);
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for (Py_ssize_t i = 0; i < TABLE_SIZE; i++) {
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p->table[i] = Py_SAFE_DOWNCAST(not_found_shift,
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Py_ssize_t, SHIFT_TYPE);
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}
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for (Py_ssize_t i = len_needle - not_found_shift; i < len_needle; i++) {
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SHIFT_TYPE shift = Py_SAFE_DOWNCAST(len_needle - 1 - i,
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Py_ssize_t, SHIFT_TYPE);
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p->table[needle[i] & TABLE_MASK] = shift;
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}
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}
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Py_LOCAL_INLINE(Py_ssize_t)
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static Py_ssize_t
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STRINGLIB(_two_way)(const STRINGLIB_CHAR *haystack, Py_ssize_t len_haystack,
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STRINGLIB(prework) *p)
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{
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// Crochemore and Perrin's (1991) Two-Way algorithm.
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// See http://www-igm.univ-mlv.fr/~lecroq/string/node26.html#SECTION00260
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Py_ssize_t len_needle = p->len_needle;
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Py_ssize_t cut = p->cut;
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const Py_ssize_t len_needle = p->len_needle;
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const Py_ssize_t cut = p->cut;
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Py_ssize_t period = p->period;
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const STRINGLIB_CHAR *needle = p->needle;
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const STRINGLIB_CHAR *window = haystack;
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const STRINGLIB_CHAR *last_window = haystack + len_haystack - len_needle;
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const STRINGLIB_CHAR *const needle = p->needle;
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const STRINGLIB_CHAR *window_last = haystack + len_needle - 1;
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const STRINGLIB_CHAR *const haystack_end = haystack + len_haystack;
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SHIFT_TYPE *table = p->table;
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const STRINGLIB_CHAR *window;
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LOG("===== Two-way: \"%s\" in \"%s\". =====\n", needle, haystack);
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if (p->is_periodic) {
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LOG("Needle is periodic.\n");
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Py_ssize_t memory = 0;
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periodicwindowloop:
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while (window <= last_window) {
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Py_ssize_t i = Py_MAX(cut, memory);
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// Visualize the line-up:
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LOG("> "); LOG_STRING(haystack, len_haystack);
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LOG("\n> "); LOG("%*s", window - haystack, "");
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LOG_STRING(needle, len_needle);
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LOG("\n> "); LOG("%*s", window - haystack + i, "");
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LOG(" ^ <-- cut\n");
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if (window[i] != needle[i]) {
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// Sunday's trick: if we're going to jump, we might
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// as well jump to line up the character *after* the
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// current window.
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STRINGLIB_CHAR first_outside = window[len_needle];
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SHIFT_TYPE shift = table[first_outside & TABLE_MASK];
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if (shift == NOT_FOUND) {
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LOG("\"%c\" not found. Skipping entirely.\n",
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first_outside);
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window += len_needle + 1;
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while (window_last < haystack_end) {
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assert(memory == 0);
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for (;;) {
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LOG_LINEUP();
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Py_ssize_t shift = table[(*window_last) & TABLE_MASK];
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window_last += shift;
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if (shift == 0) {
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break;
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}
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else {
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LOG("Shifting to line up \"%c\".\n", first_outside);
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Py_ssize_t memory_shift = i - cut + 1;
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window += Py_MAX(shift, memory_shift);
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if (window_last >= haystack_end) {
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return -1;
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}
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memory = 0;
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goto periodicwindowloop;
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LOG("Horspool skip");
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}
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for (i = i + 1; i < len_needle; i++) {
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no_shift:
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window = window_last - len_needle + 1;
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assert((window[len_needle - 1] & TABLE_MASK) ==
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(needle[len_needle - 1] & TABLE_MASK));
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Py_ssize_t i = Py_MAX(cut, memory);
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for (; i < len_needle; i++) {
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if (needle[i] != window[i]) {
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LOG("Right half does not match. Jump ahead by %d.\n",
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i - cut + 1);
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window += i - cut + 1;
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LOG("Right half does not match.\n");
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window_last += i - cut + 1;
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memory = 0;
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goto periodicwindowloop;
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}
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}
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for (i = memory; i < cut; i++) {
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if (needle[i] != window[i]) {
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LOG("Left half does not match. Jump ahead by period %d.\n",
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period);
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window += period;
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LOG("Left half does not match.\n");
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window_last += period;
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memory = len_needle - period;
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goto periodicwindowloop;
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if (window_last >= haystack_end) {
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return -1;
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}
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Py_ssize_t shift = table[(*window_last) & TABLE_MASK];
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if (shift) {
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// A mismatch has been identified to the right
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// of where i will next start, so we can jump
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// at least as far as if the mismatch occurred
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// on the first comparison.
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Py_ssize_t mem_jump = Py_MAX(cut, memory) - cut + 1;
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LOG("Skip with Memory.\n");
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memory = 0;
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window_last += Py_MAX(shift, mem_jump);
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goto periodicwindowloop;
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}
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goto no_shift;
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}
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}
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LOG("Left half matches. Returning %d.\n",
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window - haystack);
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LOG("Found a match!\n");
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return window - haystack;
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}
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}
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else {
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Py_ssize_t gap = p->gap;
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period = Py_MAX(gap, period);
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LOG("Needle is not periodic.\n");
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assert(cut < len_needle);
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STRINGLIB_CHAR needle_cut = needle[cut];
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Py_ssize_t gap_jump_end = Py_MIN(len_needle, cut + gap);
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windowloop:
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while (window <= last_window) {
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// Visualize the line-up:
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LOG("> "); LOG_STRING(haystack, len_haystack);
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LOG("\n> "); LOG("%*s", window - haystack, "");
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LOG_STRING(needle, len_needle);
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LOG("\n> "); LOG("%*s", window - haystack + cut, "");
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LOG(" ^ <-- cut\n");
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if (window[cut] != needle_cut) {
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// Sunday's trick: if we're going to jump, we might
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// as well jump to line up the character *after* the
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// current window.
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STRINGLIB_CHAR first_outside = window[len_needle];
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SHIFT_TYPE shift = table[first_outside & TABLE_MASK];
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if (shift == NOT_FOUND) {
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LOG("\"%c\" not found. Skipping entirely.\n",
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first_outside);
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window += len_needle + 1;
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while (window_last < haystack_end) {
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for (;;) {
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LOG_LINEUP();
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Py_ssize_t shift = table[(*window_last) & TABLE_MASK];
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window_last += shift;
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if (shift == 0) {
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break;
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}
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else {
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LOG("Shifting to line up \"%c\".\n", first_outside);
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window += shift;
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if (window_last >= haystack_end) {
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return -1;
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}
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goto windowloop;
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LOG("Horspool skip");
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}
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for (Py_ssize_t i = cut + 1; i < len_needle; i++) {
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window = window_last - len_needle + 1;
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assert((window[len_needle - 1] & TABLE_MASK) ==
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(needle[len_needle - 1] & TABLE_MASK));
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for (Py_ssize_t i = cut; i < gap_jump_end; i++) {
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if (needle[i] != window[i]) {
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LOG("Right half does not match. Advance by %d.\n",
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i - cut + 1);
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window += i - cut + 1;
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LOG("Early right half mismatch: jump by gap.\n");
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assert(gap >= i - cut + 1);
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window_last += gap;
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goto windowloop;
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}
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}
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for (Py_ssize_t i = gap_jump_end; i < len_needle; i++) {
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if (needle[i] != window[i]) {
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LOG("Late right half mismatch.\n");
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assert(i - cut + 1 > gap);
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window_last += i - cut + 1;
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goto windowloop;
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}
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}
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for (Py_ssize_t i = 0; i < cut; i++) {
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if (needle[i] != window[i]) {
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LOG("Left half does not match. Advance by period %d.\n",
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period);
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window += period;
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LOG("Left half does not match.\n");
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window_last += period;
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goto windowloop;
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}
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}
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LOG("Left half matches. Returning %d.\n", window - haystack);
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LOG("Found a match!\n");
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return window - haystack;
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}
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}
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@ -465,7 +483,8 @@ STRINGLIB(_two_way)(const STRINGLIB_CHAR *haystack, Py_ssize_t len_haystack,
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return -1;
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}
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Py_LOCAL_INLINE(Py_ssize_t)
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static Py_ssize_t
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STRINGLIB(_two_way_find)(const STRINGLIB_CHAR *haystack,
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Py_ssize_t len_haystack,
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const STRINGLIB_CHAR *needle,
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@ -477,7 +496,8 @@ STRINGLIB(_two_way_find)(const STRINGLIB_CHAR *haystack,
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return STRINGLIB(_two_way)(haystack, len_haystack, &p);
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}
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Py_LOCAL_INLINE(Py_ssize_t)
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static Py_ssize_t
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STRINGLIB(_two_way_count)(const STRINGLIB_CHAR *haystack,
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Py_ssize_t len_haystack,
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const STRINGLIB_CHAR *needle,
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@ -513,47 +533,238 @@ STRINGLIB(_two_way_count)(const STRINGLIB_CHAR *haystack,
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#undef LOG
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#undef LOG_STRING
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#undef LOG_LINEUP
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static inline Py_ssize_t
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STRINGLIB(default_find)(const STRINGLIB_CHAR* s, Py_ssize_t n,
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const STRINGLIB_CHAR* p, Py_ssize_t m,
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Py_ssize_t maxcount, int mode)
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{
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const Py_ssize_t w = n - m;
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Py_ssize_t mlast = m - 1, count = 0;
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Py_ssize_t gap = mlast;
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const STRINGLIB_CHAR last = p[mlast];
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const STRINGLIB_CHAR *const ss = &s[mlast];
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unsigned long mask = 0;
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for (Py_ssize_t i = 0; i < mlast; i++) {
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STRINGLIB_BLOOM_ADD(mask, p[i]);
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if (p[i] == last) {
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gap = mlast - i - 1;
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}
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}
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STRINGLIB_BLOOM_ADD(mask, last);
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for (Py_ssize_t i = 0; i <= w; i++) {
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if (ss[i] == last) {
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/* candidate match */
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Py_ssize_t j;
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for (j = 0; j < mlast; j++) {
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if (s[i+j] != p[j]) {
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break;
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}
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}
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if (j == mlast) {
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/* got a match! */
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if (mode != FAST_COUNT) {
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return i;
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}
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count++;
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if (count == maxcount) {
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return maxcount;
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}
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i = i + mlast;
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continue;
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}
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/* miss: check if next character is part of pattern */
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if (!STRINGLIB_BLOOM(mask, ss[i+1])) {
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i = i + m;
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}
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else {
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i = i + gap;
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}
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}
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else {
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/* skip: check if next character is part of pattern */
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if (!STRINGLIB_BLOOM(mask, ss[i+1])) {
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i = i + m;
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}
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}
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}
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return mode == FAST_COUNT ? count : -1;
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}
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static Py_ssize_t
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STRINGLIB(adaptive_find)(const STRINGLIB_CHAR* s, Py_ssize_t n,
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const STRINGLIB_CHAR* p, Py_ssize_t m,
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Py_ssize_t maxcount, int mode)
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{
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const Py_ssize_t w = n - m;
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Py_ssize_t mlast = m - 1, count = 0;
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Py_ssize_t gap = mlast;
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Py_ssize_t hits = 0, res;
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const STRINGLIB_CHAR last = p[mlast];
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const STRINGLIB_CHAR *const ss = &s[mlast];
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unsigned long mask = 0;
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for (Py_ssize_t i = 0; i < mlast; i++) {
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STRINGLIB_BLOOM_ADD(mask, p[i]);
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if (p[i] == last) {
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gap = mlast - i - 1;
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}
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}
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STRINGLIB_BLOOM_ADD(mask, last);
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for (Py_ssize_t i = 0; i <= w; i++) {
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if (ss[i] == last) {
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/* candidate match */
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Py_ssize_t j;
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for (j = 0; j < mlast; j++) {
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if (s[i+j] != p[j]) {
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break;
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}
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}
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if (j == mlast) {
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/* got a match! */
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if (mode != FAST_COUNT) {
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return i;
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}
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count++;
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if (count == maxcount) {
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return maxcount;
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}
|
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i = i + mlast;
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continue;
|
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}
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hits += j + 1;
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if (hits > m / 4 && w - i > 2000) {
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if (mode == FAST_SEARCH) {
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res = STRINGLIB(_two_way_find)(s + i, n - i, p, m);
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return res == -1 ? -1 : res + i;
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}
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else {
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res = STRINGLIB(_two_way_count)(s + i, n - i, p, m,
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maxcount - count);
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return res + count;
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}
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}
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/* miss: check if next character is part of pattern */
|
||||
if (!STRINGLIB_BLOOM(mask, ss[i+1])) {
|
||||
i = i + m;
|
||||
}
|
||||
else {
|
||||
i = i + gap;
|
||||
}
|
||||
}
|
||||
else {
|
||||
/* skip: check if next character is part of pattern */
|
||||
if (!STRINGLIB_BLOOM(mask, ss[i+1])) {
|
||||
i = i + m;
|
||||
}
|
||||
}
|
||||
}
|
||||
return mode == FAST_COUNT ? count : -1;
|
||||
}
|
||||
|
||||
|
||||
static Py_ssize_t
|
||||
STRINGLIB(default_rfind)(const STRINGLIB_CHAR* s, Py_ssize_t n,
|
||||
const STRINGLIB_CHAR* p, Py_ssize_t m,
|
||||
Py_ssize_t maxcount, int mode)
|
||||
{
|
||||
/* create compressed boyer-moore delta 1 table */
|
||||
unsigned long mask = 0;
|
||||
Py_ssize_t i, j, mlast = m - 1, skip = m - 1, w = n - m;
|
||||
|
||||
/* process pattern[0] outside the loop */
|
||||
STRINGLIB_BLOOM_ADD(mask, p[0]);
|
||||
/* process pattern[:0:-1] */
|
||||
for (i = mlast; i > 0; i--) {
|
||||
STRINGLIB_BLOOM_ADD(mask, p[i]);
|
||||
if (p[i] == p[0]) {
|
||||
skip = i - 1;
|
||||
}
|
||||
}
|
||||
|
||||
for (i = w; i >= 0; i--) {
|
||||
if (s[i] == p[0]) {
|
||||
/* candidate match */
|
||||
for (j = mlast; j > 0; j--) {
|
||||
if (s[i+j] != p[j]) {
|
||||
break;
|
||||
}
|
||||
}
|
||||
if (j == 0) {
|
||||
/* got a match! */
|
||||
return i;
|
||||
}
|
||||
/* miss: check if previous character is part of pattern */
|
||||
if (i > 0 && !STRINGLIB_BLOOM(mask, s[i-1])) {
|
||||
i = i - m;
|
||||
}
|
||||
else {
|
||||
i = i - skip;
|
||||
}
|
||||
}
|
||||
else {
|
||||
/* skip: check if previous character is part of pattern */
|
||||
if (i > 0 && !STRINGLIB_BLOOM(mask, s[i-1])) {
|
||||
i = i - m;
|
||||
}
|
||||
}
|
||||
}
|
||||
return -1;
|
||||
}
|
||||
|
||||
|
||||
static inline Py_ssize_t
|
||||
STRINGLIB(count_char)(const STRINGLIB_CHAR *s, Py_ssize_t n,
|
||||
const STRINGLIB_CHAR p0, Py_ssize_t maxcount)
|
||||
{
|
||||
Py_ssize_t i, count = 0;
|
||||
for (i = 0; i < n; i++) {
|
||||
if (s[i] == p0) {
|
||||
count++;
|
||||
if (count == maxcount) {
|
||||
return maxcount;
|
||||
}
|
||||
}
|
||||
}
|
||||
return count;
|
||||
}
|
||||
|
||||
|
||||
Py_LOCAL_INLINE(Py_ssize_t)
|
||||
FASTSEARCH(const STRINGLIB_CHAR* s, Py_ssize_t n,
|
||||
const STRINGLIB_CHAR* p, Py_ssize_t m,
|
||||
Py_ssize_t maxcount, int mode)
|
||||
{
|
||||
unsigned long mask;
|
||||
Py_ssize_t skip, count = 0;
|
||||
Py_ssize_t i, j, mlast, w;
|
||||
|
||||
w = n - m;
|
||||
|
||||
if (w < 0 || (mode == FAST_COUNT && maxcount == 0))
|
||||
if (n < m || (mode == FAST_COUNT && maxcount == 0)) {
|
||||
return -1;
|
||||
}
|
||||
|
||||
/* look for special cases */
|
||||
if (m <= 1) {
|
||||
if (m <= 0)
|
||||
if (m <= 0) {
|
||||
return -1;
|
||||
}
|
||||
/* use special case for 1-character strings */
|
||||
if (mode == FAST_SEARCH)
|
||||
return STRINGLIB(find_char)(s, n, p[0]);
|
||||
else if (mode == FAST_RSEARCH)
|
||||
return STRINGLIB(rfind_char)(s, n, p[0]);
|
||||
else { /* FAST_COUNT */
|
||||
for (i = 0; i < n; i++)
|
||||
if (s[i] == p[0]) {
|
||||
count++;
|
||||
if (count == maxcount)
|
||||
return maxcount;
|
||||
}
|
||||
return count;
|
||||
else {
|
||||
return STRINGLIB(count_char)(s, n, p[0], maxcount);
|
||||
}
|
||||
}
|
||||
|
||||
mlast = m - 1;
|
||||
skip = mlast;
|
||||
mask = 0;
|
||||
|
||||
if (mode != FAST_RSEARCH) {
|
||||
if (m >= 100 && w >= 2000 && w / m >= 5) {
|
||||
if (n < 2500 || (m < 100 && n < 30000) || m < 6) {
|
||||
return STRINGLIB(default_find)(s, n, p, m, maxcount, mode);
|
||||
}
|
||||
else if ((m >> 2) * 3 < (n >> 2)) {
|
||||
/* 33% threshold, but don't overflow. */
|
||||
/* For larger problems where the needle isn't a huge
|
||||
percentage of the size of the haystack, the relatively
|
||||
expensive O(m) startup cost of the two-way algorithm
|
||||
|
|
@ -565,170 +776,18 @@ FASTSEARCH(const STRINGLIB_CHAR* s, Py_ssize_t n,
|
|||
return STRINGLIB(_two_way_count)(s, n, p, m, maxcount);
|
||||
}
|
||||
}
|
||||
const STRINGLIB_CHAR *ss = s + m - 1;
|
||||
const STRINGLIB_CHAR *pp = p + m - 1;
|
||||
|
||||
/* create compressed boyer-moore delta 1 table */
|
||||
|
||||
/* process pattern[:-1] */
|
||||
for (i = 0; i < mlast; i++) {
|
||||
STRINGLIB_BLOOM_ADD(mask, p[i]);
|
||||
if (p[i] == p[mlast]) {
|
||||
skip = mlast - i - 1;
|
||||
}
|
||||
}
|
||||
/* process pattern[-1] outside the loop */
|
||||
STRINGLIB_BLOOM_ADD(mask, p[mlast]);
|
||||
|
||||
if (m >= 100 && w >= 8000) {
|
||||
else {
|
||||
/* To ensure that we have good worst-case behavior,
|
||||
here's an adaptive version of the algorithm, where if
|
||||
we match O(m) characters without any matches of the
|
||||
entire needle, then we predict that the startup cost of
|
||||
the two-way algorithm will probably be worth it. */
|
||||
Py_ssize_t hits = 0;
|
||||
for (i = 0; i <= w; i++) {
|
||||
if (ss[i] == pp[0]) {
|
||||
/* candidate match */
|
||||
for (j = 0; j < mlast; j++) {
|
||||
if (s[i+j] != p[j]) {
|
||||
break;
|
||||
}
|
||||
}
|
||||
if (j == mlast) {
|
||||
/* got a match! */
|
||||
if (mode != FAST_COUNT) {
|
||||
return i;
|
||||
}
|
||||
count++;
|
||||
if (count == maxcount) {
|
||||
return maxcount;
|
||||
}
|
||||
i = i + mlast;
|
||||
continue;
|
||||
}
|
||||
/* miss: check if next character is part of pattern */
|
||||
if (!STRINGLIB_BLOOM(mask, ss[i+1])) {
|
||||
i = i + m;
|
||||
}
|
||||
else {
|
||||
i = i + skip;
|
||||
}
|
||||
hits += j + 1;
|
||||
if (hits >= m / 4 && i < w - 1000) {
|
||||
/* We've done O(m) fruitless comparisons
|
||||
anyway, so spend the O(m) cost on the
|
||||
setup for the two-way algorithm. */
|
||||
Py_ssize_t res;
|
||||
if (mode == FAST_COUNT) {
|
||||
res = STRINGLIB(_two_way_count)(
|
||||
s+i, n-i, p, m, maxcount-count);
|
||||
return count + res;
|
||||
}
|
||||
else {
|
||||
res = STRINGLIB(_two_way_find)(s+i, n-i, p, m);
|
||||
if (res == -1) {
|
||||
return -1;
|
||||
}
|
||||
return i + res;
|
||||
}
|
||||
}
|
||||
}
|
||||
else {
|
||||
/* skip: check if next character is part of pattern */
|
||||
if (!STRINGLIB_BLOOM(mask, ss[i+1])) {
|
||||
i = i + m;
|
||||
}
|
||||
}
|
||||
}
|
||||
if (mode != FAST_COUNT) {
|
||||
return -1;
|
||||
}
|
||||
return count;
|
||||
}
|
||||
/* The standard, non-adaptive version of the algorithm. */
|
||||
for (i = 0; i <= w; i++) {
|
||||
/* note: using mlast in the skip path slows things down on x86 */
|
||||
if (ss[i] == pp[0]) {
|
||||
/* candidate match */
|
||||
for (j = 0; j < mlast; j++) {
|
||||
if (s[i+j] != p[j]) {
|
||||
break;
|
||||
}
|
||||
}
|
||||
if (j == mlast) {
|
||||
/* got a match! */
|
||||
if (mode != FAST_COUNT) {
|
||||
return i;
|
||||
}
|
||||
count++;
|
||||
if (count == maxcount) {
|
||||
return maxcount;
|
||||
}
|
||||
i = i + mlast;
|
||||
continue;
|
||||
}
|
||||
/* miss: check if next character is part of pattern */
|
||||
if (!STRINGLIB_BLOOM(mask, ss[i+1])) {
|
||||
i = i + m;
|
||||
}
|
||||
else {
|
||||
i = i + skip;
|
||||
}
|
||||
}
|
||||
else {
|
||||
/* skip: check if next character is part of pattern */
|
||||
if (!STRINGLIB_BLOOM(mask, ss[i+1])) {
|
||||
i = i + m;
|
||||
}
|
||||
}
|
||||
return STRINGLIB(adaptive_find)(s, n, p, m, maxcount, mode);
|
||||
}
|
||||
}
|
||||
else { /* FAST_RSEARCH */
|
||||
|
||||
/* create compressed boyer-moore delta 1 table */
|
||||
|
||||
/* process pattern[0] outside the loop */
|
||||
STRINGLIB_BLOOM_ADD(mask, p[0]);
|
||||
/* process pattern[:0:-1] */
|
||||
for (i = mlast; i > 0; i--) {
|
||||
STRINGLIB_BLOOM_ADD(mask, p[i]);
|
||||
if (p[i] == p[0]) {
|
||||
skip = i - 1;
|
||||
}
|
||||
}
|
||||
|
||||
for (i = w; i >= 0; i--) {
|
||||
if (s[i] == p[0]) {
|
||||
/* candidate match */
|
||||
for (j = mlast; j > 0; j--) {
|
||||
if (s[i+j] != p[j]) {
|
||||
break;
|
||||
}
|
||||
}
|
||||
if (j == 0) {
|
||||
/* got a match! */
|
||||
return i;
|
||||
}
|
||||
/* miss: check if previous character is part of pattern */
|
||||
if (i > 0 && !STRINGLIB_BLOOM(mask, s[i-1])) {
|
||||
i = i - m;
|
||||
}
|
||||
else {
|
||||
i = i - skip;
|
||||
}
|
||||
}
|
||||
else {
|
||||
/* skip: check if previous character is part of pattern */
|
||||
if (i > 0 && !STRINGLIB_BLOOM(mask, s[i-1])) {
|
||||
i = i - m;
|
||||
}
|
||||
}
|
||||
}
|
||||
else {
|
||||
/* FAST_RSEARCH */
|
||||
return STRINGLIB(default_rfind)(s, n, p, m, maxcount, mode);
|
||||
}
|
||||
|
||||
if (mode != FAST_COUNT)
|
||||
return -1;
|
||||
return count;
|
||||
}
|
||||
|
||||
|
|
|
|||
Loading…
Reference in New Issue