Add http_strncasecmp(3)

POSIX.1-2008 does not any locale-specific version of strncasecmp(3), so
conversions to lowercase depend on the system locale.

Since HTTP header fields must be checked without case sensitivity and
not depend on the system locale, a specialised function that forces the
"POSIX" locale is required.

1 files changed, 37 insertions, 4 deletions

diff --git a/http.c b/http.c
index 261dcc0..c3c36b2 100644
--- a/http.c
+++ b/http.c
@@ -4,6 +4,7 @@
 #include <dynstr.h>
 #include <sys/types.h>
 #include <unistd.h>
+#include <ctype.h>
 #include <errno.h>
 #include <inttypes.h>
 #include <locale.h>
@@ -1592,13 +1593,18 @@ static int process_header(struct http_ctx *const h, const char *const line,
         const struct header *const hdr = &headers[i];
         int ret;
 
-        if (!strncasecmp(line, hdr->header, n))
+        if ((ret = http_strncasecmp(line, hdr->header, n)))
         {
-            if ((ret = hdr->f(h, value)))
+            if (ret < 0)
+            {
+                fprintf(stderr, "%s: http_strncasecmp failed\n", __func__);
                 return ret;
-
-            break;
+            }
         }
+        else if ((ret = hdr->f(h, value)))
+            return ret;
+        else
+            break;
     }
 
     return append_header(h, line, n, value);
@@ -2968,3 +2974,30 @@ end:
 
     return ret;
 }
+
+int http_strncasecmp(const char *s1, const char *s2, const size_t n)
+{
+    int ret = -1;
+    const locale_t l = newlocale(LC_CTYPE_MASK, "POSIX", (locale_t)0);
+
+    if (l == (locale_t)0)
+    {
+        fprintf(stderr, "%s: newlocale(3): %s\n", __func__, strerror(errno));
+        goto end;
+    }
+
+    for (size_t i = 0; i < n; i++, s1++, s2++)
+        if (!*s1 || !*s2 || tolower_l(*s1, l) != tolower_l(*s2, l))
+        {
+            ret = 1;
+            goto end;
+        }
+
+    ret = 0;
+
+end:
+    if (l != (locale_t)0)
+        freelocale(l);
+
+    return ret;
+}