Sanitise locale code, comments and documentation

1 files changed, 44 insertions, 26 deletions

diff --git a/fpconv.c b/fpconv.c
index fd4deb0..3bcef41 100644
--- a/fpconv.c
+++ b/fpconv.c
@@ -1,3 +1,9 @@
+/* JSON uses a '.' decimal separator. strtod() / sprintf() under C libraries
+ * with locale support will break when the decimal separator is a comma.
+ *
+ * fpconv_* will around these issues with a translation buffer if required.
+ */
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <assert.h>
@@ -5,15 +11,21 @@
 
 #include "fpconv.h"
 
+/* Lua CJSON assumes the locale is the same for all threads within a
+ * process and doesn't change after initialisation.
+ *
+ * This avoids the need for per thread storage or expensive checks
+ * for call. */
 static char locale_decimal_point = '.';
 
 /* In theory multibyte decimal_points are possible, but
  * Lua CJSON only supports UTF-8 and known locales only have
  * single byte decimal points ([.,]).
  *
- * localconv() may not be thread safe, and nl_langinfo() is not
- * supported on some platforms. Use sprintf() instead. */
-void fpconv_update_locale()
+ * localconv() may not be thread safe (=>crash), and nl_langinfo() is
+ * not supported on some platforms. Use sprintf() instead - if the
+ * locale does change, at least Lua CJSON won't crash. */
+static void fpconv_update_locale()
 {
     char buf[8];
 
@@ -29,11 +41,14 @@ void fpconv_update_locale()
     locale_decimal_point = buf[1];
 }
 
-/* Check for a valid number character: [-+0-9a-fA-FpPxX.]
- * It doesn't matter if actual invalid characters are counted - strtod()
- * will find the valid number if it exists. The risk is that slightly more
- * memory might be allocated before a parse error occurs. */
-static int valid_number_character(char ch)
+/* Check for a valid number character: [-+0-9a-yA-Y.]
+ * Eg: -0.6e+5, infinity, 0xF0.F0pF0
+ *
+ * Used to find the probable end of a number. It doesn't matter if
+ * invalid characters are counted - strtod() will find the valid
+ * number if it exists.  The risk is that slightly more memory might
+ * be allocated before a parse error occurs. */
+static inline int valid_number_character(char ch)
 {
     char lower_ch;
 
@@ -42,9 +57,7 @@ static int valid_number_character(char ch)
     if (ch == '-' || ch == '+' || ch == '.')
         return 1;
 
-    /* Hex digits, exponent (e), base (p), "infinity",..
-     * The main purpose is to not include a "comma". If any other invalid
-     * characters are included, the will only generate a parse error later. */
+    /* Hex digits, exponent (e), base (p), "infinity",.. */
     lower_ch = ch | 0x20;
     if ('a' <= lower_ch && lower_ch <= 'y')
         return 1;
@@ -52,8 +65,8 @@ static int valid_number_character(char ch)
     return 0;
 }
 
-/* Calculate the size of the buffer required for a locale
- * conversion. Returns 0 if conversion is not required */
+/* Calculate the size of the buffer required for a strtod locale
+ * conversion. */
 static int strtod_buffer_size(const char *s)
 {
     const char *p = s;
@@ -68,38 +81,38 @@ static int strtod_buffer_size(const char *s)
  * character. Guaranteed to be called at the start of any valid number in a string */
 double fpconv_strtod(const char *nptr, char **endptr)
 {
-    char *num, *endnum, *dp;
-    int numlen;
+    char *buf, *endbuf, *dp;
+    int buflen;
     double value;
 
     /* System strtod() is fine when decimal point is '.' */
     if (locale_decimal_point == '.')
         return strtod(nptr, endptr);
 
-    numlen = strtod_buffer_size(nptr);
-    if (!numlen) {
+    buflen = strtod_buffer_size(nptr);
+    if (!buflen) {
         /* No valid characters found, standard strtod() return */
         *endptr = (char *)nptr;
         return 0;
     }
 
     /* Duplicate number into buffer */
-    num = malloc(numlen + 1);
-    if (!num) {
+    buf = malloc(buflen + 1);
+    if (!buf) {
         fprintf(stderr, "Out of memory");
         abort();
     }
-    memcpy(num, nptr, numlen);
-    num[numlen] = 0;
+    memcpy(buf, nptr, buflen);
+    buf[buflen] = 0;
 
     /* Update decimal point character if found */
-    dp = strchr(num, '.');
+    dp = strchr(buf, '.');
     if (dp)
         *dp = locale_decimal_point;
 
-    value = strtod(num, &endnum);
-    *endptr = (char *)&nptr[endnum - num];
-    free(num);
+    value = strtod(buf, &endbuf);
+    *endptr = (char *)&nptr[endbuf - buf];
+    free(buf);
 
     return value;
 }
@@ -142,7 +155,7 @@ int fpconv_g_fmt(char *str, double num, int precision)
     /* snprintf() to a buffer then translate for other decimal point characters */
     len = snprintf(buf, FPCONV_G_FMT_BUFSIZE, fmt, num);
 
-    /* Returned 'len' includes the null terminator */
+    /* Copy into target location. Translate decimal point if required */
     b = buf;
     do {
         *str++ = (*b == locale_decimal_point ? '.' : *b);
@@ -151,5 +164,10 @@ int fpconv_g_fmt(char *str, double num, int precision)
     return len;
 }
 
+void fpconv_init()
+{
+    fpconv_update_locale();
+}
+
 /* vi:ai et sw=4 ts=4:
  */