From ca33af45434be98d3c412e93fb6768aafa418158 Mon Sep 17 00:00:00 2001
From: Jan Breuer <jan.breuer@jaybee.cz>
Date: 周六, 20 2月 2016 23:59:50 +0800
Subject: [PATCH] Optimize #49 memory consumption of double to string conversion
---
libscpi/src/utils.c | 51 +++++++++++++++++++++++++++++----------------------
1 files changed, 29 insertions(+), 22 deletions(-)
diff --git a/libscpi/src/utils.c b/libscpi/src/utils.c
index 6d67793..dd8e042 100644
--- a/libscpi/src/utils.c
+++ b/libscpi/src/utils.c
@@ -780,67 +780,74 @@
// SUCH DAMAGE.
static char *scpi_ecvt(double arg, int ndigits, int *decpt, int *sign, char *buf, size_t bufsize) {
- int r2;
+ int r1, r2;
double fi, fj;
- char *p, *p1;
+ int w1, w2;
if (ndigits < 0) ndigits = 0;
if (ndigits >= (int) (bufsize - 1)) ndigits = bufsize - 2;
+
r2 = 0;
*sign = 0;
- p = &buf[0];
+ w1 = 0;
if (arg < 0) {
*sign = 1;
arg = -arg;
}
+ frexp(arg, &r1);
arg = modf(arg, &fi);
- p1 = &buf[bufsize];
if (fi != 0) {
- p1 = &buf[bufsize];
+ r1 = r1 * 308 / 1024 - ndigits;
+ w2 = bufsize;
+ while (r1 > 0) {
+ fj = modf(fi / 10, &fi);
+ r2++;
+ r1--;
+ }
while (fi != 0) {
fj = modf(fi / 10, &fi);
- *--p1 = (int) ((fj + .03) * 10) + '0';
+ buf[--w2] = (int) ((fj + .03) * 10) + '0';
r2++;
}
- while (p1 < &buf[bufsize]) *p++ = *p1++;
+ while (w2 < (int)bufsize) buf[w1++] = buf[w2++];
} else if (arg > 0) {
while ((fj = arg * 10) < 1) {
arg = fj;
r2--;
}
}
- p1 = &buf[ndigits];
+ w2 = ndigits;
*decpt = r2;
- if (p1 < &buf[0]) {
+ if (w2 < 0) {
buf[0] = '\0';
return buf;
}
- while (p <= p1 && p < &buf[bufsize]) {
+ while (w1 <= w2 && w1 < (int)bufsize) {
arg *= 10;
arg = modf(arg, &fj);
- *p++ = (int) fj + '0';
+ buf[w1++] = (int) fj + '0';
}
- if (p1 >= &buf[bufsize]) {
+ if (w2 >= (int)bufsize) {
buf[bufsize - 1] = '\0';
return buf;
}
- p = p1;
- *p1 += 5;
- while (*p1 > '9') {
- *p1 = '0';
- if (p1 > buf) {
- ++*--p1;
+ w1 = w2;
+ buf[w2] += 5;
+ while (buf[w2] > '9') {
+ buf[w2] = '0';
+ if (w2 > 0) {
+ ++buf[--w2];
} else {
- *p1 = '1';
+ buf[w2] = '1';
(*decpt)++;
}
}
- *p = '\0';
+ buf[w1] = '\0';
return buf;
}
-#define SCPI_DTOSTRE_BUFFER_SIZE 310
+#define SCPI_DTOSTRE_BUFFER_SIZE 32
char * SCPI_dtostre(double __val, char * __s, size_t __ssize, unsigned char __prec, unsigned char __flags) {
char buffer[SCPI_DTOSTRE_BUFFER_SIZE];
@@ -974,4 +981,4 @@
((val & 0x0000FF0000000000ul) >> 24) |
((val & 0x00FF000000000000ul) >> 40) |
((val & 0xFF00000000000000ul) >> 56);
-}
\ No newline at end of file
+}
--
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