commit 8a74c314a49ab1632f88a21970241dff0384e127
parent b4c9f249b57abb2f38e9ede0b9246d058084aa42
Author: superpozycja <anna@superpozycja.net>
Date: Sun, 1 Sep 2024 19:36:40 +0200
add utility lib for miscellaneous functions
Diffstat:
| A | lib/util.c | | | 96 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| A | lib/util.h | | | 13 | +++++++++++++ |
2 files changed, 109 insertions(+), 0 deletions(-)
diff --git a/lib/util.c b/lib/util.c
@@ -0,0 +1,96 @@
+#include "util.h"
+
+const char b64table[] =
+ "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+static int b64_chunk_to_hex(char **hex, char *b64)
+{
+ unsigned int val;
+ unsigned int sz;
+ unsigned int i;
+
+ if (strlen(b64) != 4)
+ return -1;
+
+ val = 0;
+ for (i = 0; i < 4; i++) {
+ int j = 0;
+ val <<= 6;
+
+ while (b64[i] != '=' && b64table[j] != b64[i])
+ j++;
+
+ val += j;
+ }
+
+ sz = 6 - 2 * ((b64[2] == '=') + (b64[3] == '='));
+ sz++;
+
+ *hex = (char *) malloc(sizeof(char) * sz);
+ snprintf(*hex, sz, "%0*x", sz - 1, val);
+ return 0;
+}
+
+int base64_to_hex(char **hex, char *b64)
+{
+ unsigned int len;
+
+ len = (strlen(b64) * 3 / 4) + 2;
+ *hex = (char *) malloc(sizeof(char *) * len);
+
+ for (int i = 0; i < strlen(b64)/4; i++) {
+ char b64_chunk[5];
+ char *hex_chunk;
+
+ b64_chunk[4] = '\0';
+ memcpy(b64_chunk, b64+4*i, 4);
+ b64_chunk_to_hex(&hex_chunk, b64_chunk);
+ strcat(*hex, hex_chunk);
+ }
+}
+
+int hex_to_base64(char **b64, char *hex)
+{
+ int leftover_length;
+ int block_count;
+ int res_length;
+ int length;
+ char *res;
+ int i;
+
+ length = strlen(hex);
+ block_count = length / 6;
+ leftover_length = length % 6;
+ res_length = block_count * 4;
+
+ if (leftover_length%2 == 1) {
+ fprintf(stderr, "bad sequence length\n");
+ return -1;
+ }
+
+ res = (char *) malloc(sizeof(char) * res_length + 2);
+
+ for (i = 0; i < block_count + (leftover_length != 0); i++) {
+ char block[6+1];
+ int block_hex;
+ int end_ix;
+ int j;
+
+ end_ix = i < block_count ? 6 : leftover_length;
+ memcpy(block, hex+(6*i), end_ix);
+ block[end_ix] = '\0';
+
+ block_hex = strtol(block, NULL, 16);
+ block_hex <<= 4 * (6 - end_ix);
+
+ for (j = 0; j < 4; j++) {
+ char b64;
+
+ b64 = b64table[(block_hex >> 6 * (3 - j)) & 0x3f];
+ res[4 *i + j] = j <= end_ix / 2 ? b64 : '=';
+ }
+ }
+
+ *b64 = res;
+ return 0;
+}
diff --git a/lib/util.h b/lib/util.h
@@ -0,0 +1,13 @@
+#ifndef UTIL_H
+#define UTIL_H
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+/* utility funcs */
+
+int hex_to_base64(char **b64, char *hex);
+int base64_to_hex(char **hex, char *b64);
+
+#endif
