SkUTF

Create new header and namespace, `SkUTF` where we are putting all of our
robust, well documented UTF-8, UTF-16, and UTF-32 functions:
`SkUTF::{Count,Next,To}UTF{8,16,32}()`.

SkUTF.h and SkUTF.cpp do not depend on the rest of Skia and are suitable
for re-use in other modules.

Some of the old UTF-{8,16} functions still live in SkUtils.h; their use
will be phased out in future CLs.

Also added more unit testing and cleaned up old tests.

Removed functions that were unused outside of tests or used only once.

Change-Id: Iaa59b8705abccf9c4ba082f855da368a0bad8380
Reviewed-on: https://skia-review.googlesource.com/143306
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Hal Canary <halcanary@google.com>

1 files changed, 68 insertions, 0 deletions

diff --git a/src/utils/SkUTF.h b/src/utils/SkUTF.h
new file mode 100644
index 0000000000..385102aadb
--- /dev/null
+++ b/src/utils/SkUTF.h
@@ -0,0 +1,68 @@
+// Copyright 2018 Google LLC.
+// Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
+#ifndef SkUTF_DEFINED
+#define SkUTF_DEFINED
+
+#include <cstddef>
+#include <cstdint>
+
+typedef int32_t SkUnichar;
+
+namespace SkUTF {
+
+/** Given a sequence of UTF-8 bytes, return the number of unicode codepoints.
+    If the sequence is invalid UTF-8, return -1.
+*/
+int CountUTF8(const char* utf8, size_t byteLength);
+
+/** Given a sequence of aligned UTF-16 characters in machine-endian form,
+    return the number of unicode codepoints.  If the sequence is invalid
+    UTF-16, return -1.
+*/
+int CountUTF16(const uint16_t* utf16, size_t byteLength);
+
+/** Given a sequence of aligned UTF-32 characters in machine-endian form,
+    return the number of unicode codepoints.  If the sequence is invalid
+    UTF-32, return -1.
+*/
+int CountUTF32(const int32_t* utf32, size_t byteLength);
+
+/** Given a sequence of UTF-8 bytes, return the first unicode codepoint.
+    The pointer will be incremented to point at the next codepoint's start.  If
+    invalid UTF-8 is encountered, set *ptr to end and return -1.
+*/
+SkUnichar NextUTF8(const char** ptr, const char* end);
+
+/** Given a sequence of aligned UTF-16 characters in machine-endian form,
+    return the first unicode codepoint.  The pointer will be incremented to
+    point at the next codepoint's start.  If invalid UTF-16 is encountered,
+    set *ptr to end and return -1.
+*/
+SkUnichar NextUTF16(const uint16_t** ptr, const uint16_t* end);
+
+/** Given a sequence of aligned UTF-32 characters in machine-endian form,
+    return the first unicode codepoint.  The pointer will be incremented to
+    point at the next codepoint's start.  If invalid UTF-32 is encountered,
+    set *ptr to end and return -1.
+*/
+SkUnichar NextUTF32(const int32_t** ptr, const int32_t* end);
+
+constexpr unsigned kMaxBytesInUTF8Sequence = 4;
+
+/** Convert the unicode codepoint into UTF-8.  If `utf8` is non-null, place the
+    result in that array.  Return the number of bytes in the result.  If `utf8`
+    is null, simply return the number of bytes that would be used.  For invalid
+    unicode codepoints, return 0.
+*/
+size_t ToUTF8(SkUnichar uni, char utf8[kMaxBytesInUTF8Sequence] = nullptr);
+
+/** Convert the unicode codepoint into UTF-16.  If `utf16` is non-null, place
+    the result in that array.  Return the number of UTF-16 code units in the
+    result (1 or 2).  If `utf16` is null, simply return the number of code
+    units that would be used.  For invalid unicode codepoints, return 0.
+*/
+size_t ToUTF16(SkUnichar uni, uint16_t utf16[2] = nullptr);
+
+}  // namespace SkUTF
+
+#endif  // SkUTF_DEFINED