[PATCH 1 of 2] Core: add function to decode hexadecimal strings

[Nate Karstens]

# HG changeset patch
# User Nate Karstens <nate.karstens at garmin.com>
# Date 1501265787 18000
#      Fri Jul 28 13:16:27 2017 -0500
# Node ID 7e10e1dc1fae0f538a0a74fd6783f9b33a905933
# Parent  72d3aefc2993a639cc8cddc94aefc7c4390ee252
Core: add function to decode hexadecimal strings.

Adds functionality to convert a hexadecimal string into binary data.
This will be used to decode PSKs stored in hexadecimal representation.

Signed-off-by: Nate Karstens <nate.karstens at garmin.com>

diff -r 72d3aefc2993 -r 7e10e1dc1fae src/core/ngx_string.c
--- a/src/core/ngx_string.c     Wed Jul 26 13:13:51 2017 +0300
+++ b/src/core/ngx_string.c     Fri Jul 28 13:16:27 2017 -0500
@@ -1104,6 +1104,54 @@ ngx_hextoi(u_char *line, size_t n)
 }


+ngx_int_t
+ngx_hex_decode(u_char *dst, size_t dlen, u_char *src, size_t slen)
+{
+    u_char     c, ch;
+    ngx_int_t  len;
+
+    if ((slen & 1) || (dlen < (slen / 2))) {
+        return NGX_ERROR;
+    }
+
+    len = slen / 2;
+
+    while (slen > 0) {
+        ch = *src;
+        c = (u_char) (ch | 0x20);
+
+        if (ch >= '0' && ch <= '9') {
+            *dst = ch - '0';
+        } else if (c >= 'a' && c <= 'f') {
+            *dst = c - 'a' + 10;
+        } else {
+            return NGX_ERROR;
+        }
+
+        *dst <<= 4;
+        src++;
+
+        ch = *src;
+        c = (u_char) (ch | 0x20);
+
+        if (ch >= '0' && ch <= '9') {
+            *dst |= ch - '0';
+        } else if (c >= 'a' && c <= 'f') {
+            *dst |= c - 'a' + 10;
+        } else {
+            return NGX_ERROR;
+        }
+
+        dst++;
+        src++;
+
+        slen -= 2;
+    }
+
+    return len;
+}
+
+
 u_char *
 ngx_hex_dump(u_char *dst, u_char *src, size_t len)
 {
diff -r 72d3aefc2993 -r 7e10e1dc1fae src/core/ngx_string.h
--- a/src/core/ngx_string.h     Wed Jul 26 13:13:51 2017 +0300
+++ b/src/core/ngx_string.h     Fri Jul 28 13:16:27 2017 -0500
@@ -176,6 +176,7 @@ off_t ngx_atoof(u_char *line, size_t n);
 time_t ngx_atotm(u_char *line, size_t n);
 ngx_int_t ngx_hextoi(u_char *line, size_t n);

+ngx_int_t ngx_hex_decode(u_char *dst, size_t dlen, u_char *src, size_t slen);
 u_char *ngx_hex_dump(u_char *dst, u_char *src, size_t len);



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