From fd3154f20d4c5f6e04e55d72c0b5a6312f9ce8f4 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <tridge@samba.org>
Date: Tue, 8 Nov 2011 11:04:10 +1100
Subject: [PATCH] desktop: improved ftoa_engine.c

this still doesn't perfectly match the assembler, but its closer
---
 libraries/Desktop/support/ftoa_engine.c | 74 ++++++++++++++++++++++++-
 1 file changed, 73 insertions(+), 1 deletion(-)

diff --git a/libraries/Desktop/support/ftoa_engine.c b/libraries/Desktop/support/ftoa_engine.c
index 65fa10d01d..b47baef2a3 100644
--- a/libraries/Desktop/support/ftoa_engine.c
+++ b/libraries/Desktop/support/ftoa_engine.c
@@ -1,7 +1,79 @@
 #include <stdio.h>
+#include <stdint.h>
+#include <ftoa_engine.h>
+
+/*
+ftoa: val=0.000000 prec=3 maxdgs=7 -> ret=0 flags=0x2 '0000'
+ftoa: val=inf prec=3 maxdgs=7 -> ret=38 flags=0x4 '3403'
+ftoa: val=1.000000 prec=3 maxdgs=7 -> ret=0 flags=0x0 '1000'
+ftoa: val=1.200000 prec=3 maxdgs=7 -> ret=0 flags=0x0 '1200'
+ftoa: val=1.230000 prec=3 maxdgs=7 -> ret=0 flags=0x0 '1230'
+ftoa: val=10.000000 prec=3 maxdgs=7 -> ret=1 flags=0x0 '1000'
+ftoa: val=12.000000 prec=3 maxdgs=7 -> ret=1 flags=0x0 '1200'
+ftoa: val=12.300000 prec=3 maxdgs=7 -> ret=1 flags=0x0 '1230'
+ftoa: val=101.234570 prec=3 maxdgs=7 -> ret=2 flags=0x0 '1012'
+ftoa: val=123.456790 prec=3 maxdgs=7 -> ret=2 flags=0x0 '1235'
+ftoa: val=1234.567900 prec=3 maxdgs=7 -> ret=3 flags=0x0 '1235'
+ftoa: val=1234.567900 prec=3 maxdgs=1 -> ret=3 flags=0x0 '1235'
+ftoa: val=1234.567900 prec=1 maxdgs=3 -> ret=3 flags=0x0 '12'
+ftoa: val=0.000000 prec=3 maxdgs=7 -> ret=0 flags=0x2 '0000'
+ftoa: val=0.200000 prec=3 maxdgs=7 -> ret=-1 flags=0x0 '2000'
+ftoa: val=0.230000 prec=3 maxdgs=7 -> ret=-1 flags=0x0 '2300'
+ftoa: val=0.023457 prec=3 maxdgs=7 -> ret=-2 flags=0x0 '2346'
+ftoa: val=0.002346 prec=3 maxdgs=7 -> ret=-3 flags=0x0 '2346'
+ftoa: val=0.000235 prec=3 maxdgs=7 -> ret=-4 flags=0x0 '235'
+ftoa: val=0.000023 prec=3 maxdgs=7 -> ret=-5 flags=0x0 '23'
+ftoa: val=0.000002 prec=3 maxdgs=7 -> ret=-6 flags=0x0 '2'
+ftoa: val=0.000000 prec=3 maxdgs=7 -> ret=-7 flags=0x0 '2'
+ftoa: val=0.000000 prec=3 maxdgs=7 -> ret=-8 flags=0x0 '2'
+ftoa: val=0.000000 prec=3 maxdgs=7 -> ret=-9 flags=0x0 '2'
+ftoa: val=0.200000 prec=5 maxdgs=2 -> ret=-1 flags=0x0 '2'
+ftoa: val=0.230000 prec=5 maxdgs=2 -> ret=-1 flags=0x0 '2'
+*/
 
 int __ftoa_engine(double val, char *buf,
 		  unsigned char prec, unsigned char maxdgs)
 {
-	return sprintf(buf, "%*.*lf", prec, maxdgs, val);
+	uint8_t flags = 0;
+	char tbuf[32];
+	int ret;
+
+	if (isnan(val)) {
+		buf[0] = FTOA_NAN;
+		return 0;
+	}
+	if (isinf(val)) {
+		buf[0] = FTOA_INF;
+		return 0;
+	}
+
+	buf[0] = 0;
+
+	if (val < 0.0) {
+		buf[0] |= FTOA_MINUS;
+		val = -val;
+	}
+
+	ret = -1;
+	while (val >= 1.0) {
+		val *= 0.1;
+		ret++;
+	}
+	while (val < 0.1) {
+		val *= 10.0;
+		ret--;
+		if (ret < -10) {
+			buf[0] |= FTOA_ZERO;
+			memset(&buf[1], '0', prec+1);
+			buf[1+prec+1] = 0;
+			return 0;
+		}
+	}
+	if (maxdgs == 0) {
+		snprintf(tbuf, sizeof(tbuf), "%lf", val);
+	} else {
+		snprintf(tbuf, sizeof(tbuf), "%.*lf", (int)maxdgs, val);
+	}
+	strncpy(buf+1, &tbuf[2], prec+1);
+	return ret;
 }