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Replace use of Skia's Base64 Encoding/Decoding logic with a copy of t…
…he equivalent code (flutter#46543) Skia would like to remove SkBase64.h from its public API. This ports the same functionality into Flutter's codebase with tests. The implementation was copied from [Skia](https://github.com/google/skia/blob/387853af198f03b4634239fb92cac5d49fe37100/src/utils/SkBase64.cpp) then modified to match Flutter's style and have readable tests. In a follow-up PR, I would like to add a function to pre-flight the calculation needed to figure out how many bytes are needed to be allocated, to avoid the clunky double API call (see the TODOs). I chose to put the code in `//shell/common` at the suggestion of Flutter devs, but it needs to be in its own source_set because it is used in a few other places (for now) and we want to avoid dependency cycles. ## Pre-launch Checklist - [x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [x] I read the [Tree Hygiene] wiki page, which explains my responsibilities. - [x] I read and followed the [Flutter Style Guide] and the [C++, Objective-C, Java style guides]. - [ ] I listed at least one issue that this PR fixes in the description above. - [x] I added new tests to check the change I am making or feature I am adding, or the PR is [test-exempt]. See [testing the engine] for instructions on writing and running engine tests. - [x] I updated/added relevant documentation (doc comments with `///`). - [x] I signed the [CLA]. - [x] All existing and new tests are passing. If you need help, consider asking for advice on the #hackers-new channel on [Discord]. <!-- Links --> [Contributor Guide]: https://github.com/flutter/flutter/wiki/Tree-hygiene#overview [Tree Hygiene]: https://github.com/flutter/flutter/wiki/Tree-hygiene [test-exempt]: https://github.com/flutter/flutter/wiki/Tree-hygiene#tests [Flutter Style Guide]: https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo [C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style [testing the engine]: https://github.com/flutter/flutter/wiki/Testing-the-engine [CLA]: https://cla.developers.google.com/ [flutter/tests]: https://github.com/flutter/tests [breaking change policy]: https://github.com/flutter/flutter/wiki/Tree-hygiene#handling-breaking-changes [Discord]: https://github.com/flutter/flutter/wiki/Chat
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,157 @@ | ||
| // Copyright 2013 The Flutter Authors. All rights reserved. | ||
| // Use of this source code is governed by a BSD-style license that can be | ||
| // found in the LICENSE file. | ||
|
|
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| #include "flutter/shell/common/base64.h" | ||
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| #include "flutter/fml/logging.h" | ||
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| #include <cstdint> | ||
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| #define DecodePad -2 | ||
| #define EncodePad 64 | ||
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| static const char kDefaultEncode[] = | ||
| "ABCDEFGHIJKLMNOPQRSTUVWXYZ" | ||
| "abcdefghijklmnopqrstuvwxyz" | ||
| "0123456789+/="; | ||
|
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| static const signed char kDecodeData[] = { | ||
| 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, | ||
| -1, -1, DecodePad, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, | ||
| 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, | ||
| -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, | ||
| 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51}; | ||
|
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| namespace flutter { | ||
|
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| Base64::Error Base64::Decode(const void* srcv, | ||
| size_t srcLength, | ||
| void* dstv, | ||
| size_t* dstLength) { | ||
| const unsigned char* src = static_cast<const unsigned char*>(srcv); | ||
| unsigned char* dst = static_cast<unsigned char*>(dstv); | ||
|
|
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| int i = 0; | ||
| bool padTwo = false; | ||
| bool padThree = false; | ||
| char unsigned const* const end = src + srcLength; | ||
| while (src < end) { | ||
| unsigned char bytes[4] = {0, 0, 0, 0}; | ||
| int byte = 0; | ||
| do { | ||
| unsigned char srcByte = *src++; | ||
| if (srcByte == 0) { | ||
| *dstLength = i; | ||
| return Error::kNone; | ||
| } | ||
| if (srcByte <= ' ') { | ||
| continue; // treat as white space | ||
| } | ||
| if (srcByte < '+' || srcByte > 'z') { | ||
| return Error::kBadChar; | ||
| } | ||
| signed char decoded = kDecodeData[srcByte - '+']; | ||
| bytes[byte] = decoded; | ||
| if (decoded != DecodePad) { | ||
| if (decoded < 0) { | ||
| return Error::kBadChar; | ||
| } | ||
| byte++; | ||
| if (*src) { | ||
| continue; | ||
| } | ||
| if (byte == 0) { | ||
| *dstLength = i; | ||
| return Error::kNone; | ||
| } | ||
| if (byte == 4) { | ||
| break; | ||
| } | ||
| } | ||
| // As an optimization, if we find an equals sign | ||
| // we assume all future bytes to read are the | ||
| // appropriate number of padding equals signs. | ||
| if (byte < 2) { | ||
| return Error::kBadPadding; | ||
| } | ||
| padThree = true; | ||
| if (byte == 2) { | ||
| padTwo = true; | ||
| } | ||
| break; | ||
| } while (byte < 4); | ||
| int two = 0; | ||
| int three = 0; | ||
| if (dst) { | ||
| int one = (uint8_t)(bytes[0] << 2); | ||
| two = bytes[1]; | ||
| one |= two >> 4; | ||
| two = (uint8_t)((two << 4) & 0xFF); | ||
| three = bytes[2]; | ||
| two |= three >> 2; | ||
| three = (uint8_t)((three << 6) & 0xFF); | ||
| three |= bytes[3]; | ||
| FML_DCHECK(one < 256 && two < 256 && three < 256); | ||
| dst[i] = (unsigned char)one; | ||
| } | ||
| i++; | ||
| if (padTwo) { | ||
| break; | ||
| } | ||
| if (dst) { | ||
| dst[i] = (unsigned char)two; | ||
| } | ||
| i++; | ||
| if (padThree) { | ||
| break; | ||
| } | ||
| if (dst) { | ||
| dst[i] = (unsigned char)three; | ||
| } | ||
| i++; | ||
| } | ||
| *dstLength = i; | ||
| return Error::kNone; | ||
| } | ||
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| size_t Base64::Encode(const void* srcv, size_t length, void* dstv) { | ||
| const unsigned char* src = static_cast<const unsigned char*>(srcv); | ||
| unsigned char* dst = static_cast<unsigned char*>(dstv); | ||
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| const char* encode = kDefaultEncode; | ||
| if (dst) { | ||
| size_t remainder = length % 3; | ||
| char unsigned const* const end = &src[length - remainder]; | ||
| while (src < end) { | ||
| unsigned a = *src++; | ||
| unsigned b = *src++; | ||
| unsigned c = *src++; | ||
| int d = c & 0x3F; | ||
| c = (c >> 6 | b << 2) & 0x3F; | ||
| b = (b >> 4 | a << 4) & 0x3F; | ||
| a = a >> 2; | ||
| *dst++ = encode[a]; | ||
| *dst++ = encode[b]; | ||
| *dst++ = encode[c]; | ||
| *dst++ = encode[d]; | ||
| } | ||
| if (remainder > 0) { | ||
| int k1 = 0; | ||
| int k2 = EncodePad; | ||
| int a = (uint8_t)*src++; | ||
| if (remainder == 2) { | ||
| int b = *src++; | ||
| k1 = b >> 4; | ||
| k2 = (b << 2) & 0x3F; | ||
| } | ||
| *dst++ = encode[a >> 2]; | ||
| *dst++ = encode[(k1 | a << 4) & 0x3F]; | ||
| *dst++ = encode[k2]; | ||
| *dst++ = encode[EncodePad]; | ||
| } | ||
| } | ||
| return (length + 2) / 3 * 4; | ||
| } | ||
|
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| } // namespace flutter |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,53 @@ | ||
| // Copyright 2013 The Flutter Authors. All rights reserved. | ||
| // Use of this source code is governed by a BSD-style license that can be | ||
| // found in the LICENSE file. | ||
|
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| #ifndef FLUTTER_SHELL_COMMON_BASE64_H_ | ||
| #define FLUTTER_SHELL_COMMON_BASE64_H_ | ||
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| #include <cstddef> | ||
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| namespace flutter { | ||
|
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| struct Base64 { | ||
| public: | ||
| enum class Error { | ||
| kNone, | ||
| kBadPadding, | ||
| kBadChar, | ||
| }; | ||
|
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| /** | ||
| Base64 encodes src into dst. | ||
| Normally this is called once with 'dst' nullptr to get the required size, | ||
| then again with an allocated 'dst' pointer to do the actual encoding. | ||
| @param dst nullptr or a pointer to a buffer large enough to receive the | ||
| result | ||
| @return the required length of dst for encoding. | ||
| */ | ||
| static size_t Encode(const void* src, size_t length, void* dst); | ||
|
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| /** | ||
| Base64 decodes src into dst. | ||
| Normally this is called once with 'dst' nullptr to get the required size, | ||
| then again with an allocated 'dst' pointer to do the actual encoding. | ||
| @param dst nullptr or a pointer to a buffer large enough to receive the | ||
| result | ||
| @param dstLength assigned the length dst is required to be. Must not be | ||
| nullptr. | ||
| */ | ||
| [[nodiscard]] static Error Decode(const void* src, | ||
| size_t srcLength, | ||
| void* dst, | ||
| size_t* dstLength); | ||
| }; | ||
|
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| } // namespace flutter | ||
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| #endif // FLUTTER_SHELL_COMMON_BASE64_H_ |
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