Factor out UTF-8 reading utilities

1 files changed, 99 insertions, 0 deletions

diff --git a/src/read_utf8.c b/src/read_utf8.c
new file mode 100644
index 00000000..c6a24778
--- /dev/null
+++ b/src/read_utf8.c
@@ -0,0 +1,99 @@
+// Copyright 2011-2021 David Robillard <d@drobilla.net>
+// SPDX-License-Identifier: ISC
+
+#include "read_utf8.h"
+#include "reader.h"
+
+#include "string_utils.h"
+
+#include <stdio.h>
+
+static SerdStatus
+skip_invalid_utf8(SerdReader* const reader)
+{
+  for (int b = peek_byte(reader); b != EOF && ((uint8_t)b & 0x80);) {
+    skip_byte(reader, b);
+    b = peek_byte(reader);
+  }
+
+  return reader->strict ? SERD_BAD_SYNTAX : SERD_FAILURE;
+}
+
+static SerdStatus
+bad_char(SerdReader* const reader, const char* const fmt, const uint8_t c)
+{
+  r_err(reader, SERD_BAD_SYNTAX, fmt, c);
+  return skip_invalid_utf8(reader);
+}
+
+static SerdStatus
+read_utf8_continuation_bytes(SerdReader* const reader,
+                             uint8_t           bytes[4],
+                             uint32_t* const   size,
+                             const uint8_t     lead)
+{
+  *size = utf8_num_bytes(lead);
+  if (*size < 1 || *size > 4) {
+    return bad_char(reader, "0x%X is not a UTF-8 leading byte", lead);
+  }
+
+  bytes[0] = lead;
+
+  for (uint32_t i = 1U; i < *size; ++i) {
+    const int b = peek_byte(reader);
+    if (b == EOF) {
+      return r_err(reader, SERD_NO_DATA, "unexpected end of input");
+    }
+
+    const uint8_t byte = (uint8_t)b;
+    if (!(byte & 0x80U)) {
+      return bad_char(reader, "0x%X is not a UTF-8 continuation byte", byte);
+    }
+
+    skip_byte(reader, b);
+    bytes[i] = byte;
+  }
+
+  return SERD_SUCCESS;
+}
+
+SerdStatus
+read_utf8_continuation(SerdReader* const reader,
+                       SerdNode* const   dest,
+                       const uint8_t     lead)
+{
+  uint32_t size     = 0;
+  uint8_t  bytes[8] = {lead, 0U, 0U, 0U, 0U, 0U, 0U, 0U};
+
+  SerdStatus st = read_utf8_continuation_bytes(reader, bytes, &size, lead);
+  if (st) {
+    return reader->strict ? st : push_bytes(reader, dest, replacement_char, 3);
+  }
+
+  return push_bytes(reader, dest, bytes, size);
+}
+
+SerdStatus
+read_utf8_code_point(SerdReader* const reader,
+                     SerdNode* const   dest,
+                     uint32_t* const   code,
+                     const uint8_t     lead)
+{
+  uint32_t size     = 0U;
+  uint8_t  bytes[8] = {lead, 0U, 0U, 0U, 0U, 0U, 0U, 0U};
+
+  *code = 0U;
+
+  skip_byte(reader, lead);
+
+  SerdStatus st = read_utf8_continuation_bytes(reader, bytes, &size, lead);
+  if (st) {
+    return reader->strict ? st : push_bytes(reader, dest, replacement_char, 3);
+  }
+
+  if (!(st = push_bytes(reader, dest, bytes, size))) {
+    *code = parse_counted_utf8_char(bytes, size);
+  }
+
+  return st;
+}