feat(util): add hex_encode_*() functions

util/hex.c

@@ -0,0 +1,48 @@
+#include <assert.h>
+#include <errno.h>
+#include <stddef.h>
+#include <stdlib.h>
+
+static int hex_encode(char **out, const void *ptr, size_t nbytes,
+                      const char *digits) {
+  const uint8_t *bytes;
+  char *chars;
+  size_t i;
+
+  assert(out != NULL);
+  assert(ptr != NULL);
+  assert(digits != NULL);
+
+  *out = NULL;
+  bytes = ptr;
+
+  chars = malloc(2 * nbytes + 1);
+
+  if (chars == NULL) {
+    return -ENOMEM;
+  }
+
+  for (i = 0; i < nbytes; i++) {
+    chars[i * 2 + 0] = digits[bytes[i] >> 4];
+    chars[i * 2 + 1] = digits[bytes[i] & 15];
+  }
+
+  chars[nbytes * 2] = '\0';
+  *out = chars;
+
+  return 0;
+}
+
+int hex_encode_lc(char **out, const void *bytes, size_t nbytes) {
+  assert(out != NULL);
+  assert(bytes != NULL);
+
+  return hex_encode(out, bytes, nbytes, "0123456789abcdef");
+}
+
+int hex_encode_uc(char **out, const void *bytes, size_t nbytes) {
+  assert(out != NULL);
+  assert(bytes != NULL);
+
+  return hex_encode(out, bytes, nbytes, "0123456789ABCDEF");
+}

util/hex.h

@@ -0,0 +1,6 @@
+#pragma once
+
+#include <stddef.h>
+
+int hex_encode_lc(char **out, const void *bytes, size_t nbytes);
+int hex_encode_uc(char **out, const void *bytes, size_t nbytes);

util/meson.build

@@ -8,6 +8,8 @@ util_lib = static_library(
     'crypto.h',
     'fs.c',
     'fs.h',
+    'hex.c',
+    'hex.h',
     'iobuf.c',
     'iobuf.h',
     'list.c',