1 files changed, 131 insertions, 0 deletions
diff --git a/subprojects/exess/src/hex.c b/subprojects/exess/src/hex.c
new file mode 100644
index 00000000..bd9de4d6
--- /dev/null
+++ b/subprojects/exess/src/hex.c
@@ -0,0 +1,131 @@
+/*
+  Copyright 2011-2021 David Robillard <d@drobilla.net>
+
+  Permission to use, copy, modify, and/or distribute this software for any
+  purpose with or without fee is hereby granted, provided that the above
+  copyright notice and this permission notice appear in all copies.
+
+  THIS SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+
+#include "read_utils.h"
+#include "string_utils.h"
+#include "write_utils.h"
+
+#include "exess/exess.h"
+
+#include <stdint.h>
+#include <string.h>
+
+/// Hex encoding table
+static const char hex_map[] = "0123456789ABCDEF";
+
+static inline uint8_t
+decode_nibble(const char c)
+{
+  if (is_digit(c)) {
+    return (uint8_t)(c - '0');
+  }
+
+  if (c >= 'A' && c <= 'F') {
+    return (uint8_t)(10 + c - 'A');
+  }
+
+  if (c >= 'a' && c <= 'f') {
+    return (uint8_t)(10 + c - 'a');
+  }
+
+  return UINT8_MAX;
+}
+
+static char
+next_char(const char* const str, size_t* const i)
+{
+  *i += skip_whitespace(str + *i);
+
+  return str[*i];
+}
+
+size_t
+exess_hex_decoded_size(const size_t length)
+{
+  return length / 2;
+}
+
+ExessResult
+exess_read_hex(ExessBlob* const out, const char* const str)
+{
+  uint8_t* const uout = (uint8_t*)out->data;
+  size_t         i    = 0u;
+  size_t         o    = 0u;
+
+  while (str[i]) {
+    const char hi_char = next_char(str, &i);
+    if (!hi_char) {
+      break;
+    }
+
+    ++i;
+
+    const uint8_t hi = decode_nibble(hi_char);
+    if (hi == UINT8_MAX) {
+      return result(EXESS_EXPECTED_HEX, i);
+    }
+
+    const char lo_char = next_char(str, &i);
+    if (!lo_char) {
+      return result(EXESS_EXPECTED_HEX, i);
+    }
+
+    ++i;
+
+    const uint8_t lo = decode_nibble(lo_char);
+    if (lo == UINT8_MAX) {
+      return result(EXESS_EXPECTED_HEX, i);
+    }
+
+    if (o >= out->size) {
+      return result(EXESS_NO_SPACE, i);
+    }
+
+    uout[o++] = (uint8_t)(hi << 4u) | lo;
+  }
+
+  out->size = o;
+  return result(EXESS_SUCCESS, i);
+}
+
+ExessResult
+exess_write_hex(const size_t      data_size,
+                const void* const data,
+                const size_t      buf_size,
+                char* const       buf)
+{
+  const size_t length = 2 * data_size;
+  if (!buf) {
+    return result(EXESS_SUCCESS, length);
+  }
+
+  if (buf_size < length + 1) {
+    return result(EXESS_NO_SPACE, 0);
+  }
+
+  const uint8_t* const in = (const uint8_t*)data;
+  size_t               o  = 0u;
+
+  for (size_t i = 0; i < data_size; ++i) {
+    const uint8_t hi = (in[i] & 0xF0u) >> 4u;
+    const uint8_t lo = (in[i] & 0x0Fu);
+
+    buf[o++] = hex_map[hi];
+    buf[o++] = hex_map[lo];
+  }
+
+  return end_write(EXESS_SUCCESS, buf_size, buf, o);
+}