[patch][bugfix]Http mp4: replace strtod() with improved ngx_atofp() because precision problem.

[月耳]

# HG changeset patch
# User hucongcong <hucong.c at foxmail.com>
# Date 1476342771 -28800
#      Thu Oct 13 15:12:51 2016 +0800
# Node ID 93bad8b82169245db6d4fe4e6b6c823221ee6a38
# Parent  7cdf69d012f02a80c94d930b29c71847e203e4d6
Http mp4: replace strtod() with improved ngx_atofp() because precision problem.

function prototype is ngx_atofp(u_char *line, size_t n, size_t point).
use case based on the old version:
ngx_atofp("12.2193", 7, 0) returns NGX_ERROR,
ngx_atofp("12.2193", 7, 2) returns NGX_ERROR.
now, allow point = 0 or point less than the number of fractional digits.
ngx_atofp("12.2193", 7, 0) returns 12,
ngx_atofp("12.2193", 7, 2) returns 1221.
retained all the required or right feature at the same time, e.g.,
ngx_atofp("10.5", 4, 2) returns 1050.

deprecated strtod() in ngx_http_mp4_module, since the precision problem,
which was metioned in http://stackoverflow.com/questions/18361261, e.g.,
(int) (strtod((char *) "32.480", NULL) * 1000) returns 32479.
another way to solve this problem is like this round(strtod()), e.g.,
(int) round((strtod((char *) "32.480", NULL) * 1000)) returns 32480,
but its not necessary, since we have a better ngx_atofp().

diff -r 7cdf69d012f0 -r 93bad8b82169 src/core/ngx_string.c
--- a/src/core/ngx_string.c	Tue Oct 11 18:03:01 2016 +0300
+++ b/src/core/ngx_string.c	Thu Oct 13 15:12:51 2016 +0800
@@ -945,8 +945,8 @@
 
     for (value = 0; n--; line++) {
 
-        if (point == 0) {
-            return NGX_ERROR;
+        if (dot && point == 0) {
+            break;
         }
 
         if (*line == '.') {
diff -r 7cdf69d012f0 -r 93bad8b82169 src/http/modules/ngx_http_mp4_module.c
--- a/src/http/modules/ngx_http_mp4_module.c	Tue Oct 11 18:03:01 2016 +0300
+++ b/src/http/modules/ngx_http_mp4_module.c	Thu Oct 13 15:12:51 2016 +0800
@@ -535,28 +535,14 @@
 
         if (ngx_http_arg(r, (u_char *) "start", 5, &value) == NGX_OK) {
 
-            /*
-             * A Flash player may send start value with a lot of digits
-             * after dot so strtod() is used instead of atofp().  NaNs and
-             * infinities become negative numbers after (int) conversion.
-             */
-
-            ngx_set_errno(0);
-            start = (int) (strtod((char *) value.data, NULL) * 1000);
-
-            if (ngx_errno != 0) {
-                start = -1;
-            }
+            /* start = -1 when NGX_ERROR returned by ngx_atofp */
+
+            start = ngx_atofp(value.data, value.len, 3);
         }
 
         if (ngx_http_arg(r, (u_char *) "end", 3, &value) == NGX_OK) {
 
-            ngx_set_errno(0);
-            end = (int) (strtod((char *) value.data, NULL) * 1000);
-
-            if (ngx_errno != 0) {
-                end = -1;
-            }
+            end = ngx_atofp(value.data, value.len, 3);
 
             if (end > 0) {
                 if (start < 0) {