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LZW decoder for GIF images implemented.
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| /* MIT License | ||
| * | ||
| * Copyright (c) 2019 - 2024 Andreas Merkle <[email protected]> | ||
| * | ||
| * Permission is hereby granted, free of charge, to any person obtaining a copy | ||
| * of this software and associated documentation files (the "Software"), to deal | ||
| * in the Software without restriction, including without limitation the rights | ||
| * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | ||
| * copies of the Software, and to permit persons to whom the Software is | ||
| * furnished to do so, subject to the following conditions: | ||
| * | ||
| * The above copyright notice and this permission notice shall be included in all | ||
| * copies or substantial portions of the Software. | ||
| * | ||
| * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | ||
| * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | ||
| * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | ||
| * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | ||
| * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | ||
| * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE | ||
| * SOFTWARE. | ||
| */ | ||
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| /******************************************************************************* | ||
| DESCRIPTION | ||
| *******************************************************************************/ | ||
| /** | ||
| * @brief LZW decoder for GIF images | ||
| * @author Andreas Merkle <[email protected]> | ||
| */ | ||
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| /****************************************************************************** | ||
| * Includes | ||
| *****************************************************************************/ | ||
| #include "LzwDecoder.h" | ||
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| /****************************************************************************** | ||
| * Compiler Switches | ||
| *****************************************************************************/ | ||
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| /****************************************************************************** | ||
| * Macros | ||
| *****************************************************************************/ | ||
|
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| /****************************************************************************** | ||
| * Types and classes | ||
| *****************************************************************************/ | ||
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| /****************************************************************************** | ||
| * Prototypes | ||
| *****************************************************************************/ | ||
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| /****************************************************************************** | ||
| * Local Variables | ||
| *****************************************************************************/ | ||
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| /****************************************************************************** | ||
| * Public Methods | ||
| *****************************************************************************/ | ||
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| void LzwDecoder::init(uint8_t lzwMinCodeWidth) | ||
| { | ||
| m_lzwMinCodeWidth = lzwMinCodeWidth; | ||
| m_clearCode = 1U << m_lzwMinCodeWidth; | ||
| m_endCode = m_clearCode + 1U; | ||
| m_stackPtr = m_stack; | ||
| m_bitsInBuffer = 0U; | ||
| clear(); | ||
| } | ||
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| bool LzwDecoder::decode(ReadFromInStream readFromInStreamFunc, WriteToOutStream writeToOutStreamFunc) | ||
| { | ||
| bool isSuccessful = true; | ||
| bool isEnd = false; | ||
| uint32_t code; | ||
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| if ((nullptr == m_codes) || | ||
| (nullptr == m_stack)) | ||
| { | ||
| isSuccessful = false; | ||
| } | ||
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| while((false == isEnd) && (true == isSuccessful)) | ||
| { | ||
| /* Get code */ | ||
| if (false == getCode(code, readFromInStreamFunc)) | ||
| { | ||
| isSuccessful = false; | ||
| } | ||
| else | ||
| { | ||
| /* Finished? */ | ||
| if (code == m_endCode) | ||
| { | ||
| isEnd = true; | ||
| } | ||
| /* Decoder initialization request? */ | ||
| else if (code == m_clearCode) | ||
| { | ||
| clear(); | ||
| } | ||
| /* Continuoue decompression. */ | ||
| else if (false == decompress(code, writeToOutStreamFunc)) | ||
| { | ||
| isSuccessful = false; | ||
| } | ||
| else | ||
| { | ||
| /* Go ahead. */ | ||
| ; | ||
| } | ||
| } | ||
| } | ||
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| return isSuccessful; | ||
| } | ||
|
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| /****************************************************************************** | ||
| * Protected Methods | ||
| *****************************************************************************/ | ||
|
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| /****************************************************************************** | ||
| * Private Methods | ||
| *****************************************************************************/ | ||
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| void LzwDecoder::clear() | ||
| { | ||
| m_nextCode = m_endCode + 1U; | ||
| m_maxCode = 2U * m_clearCode - 1U; | ||
| m_codeWidth = m_lzwMinCodeWidth + 1U; | ||
| m_isInitialState = true; | ||
| } | ||
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| bool LzwDecoder::getCode(uint32_t& code, ReadFromInStream readFromInStreamFunc) | ||
| { | ||
| bool isSuccessful = true; | ||
| size_t codeBufferIdx = 0U; | ||
| uint32_t codeBitsNeeded = m_codeWidth; | ||
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| code = 0U; | ||
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| /* Run as long as code bits are still needed. */ | ||
| while((0U < codeBitsNeeded) && (true == isSuccessful)) | ||
| { | ||
| /* No bits in the buffer anymore? */ | ||
| if (0U == m_bitsInBuffer) | ||
| { | ||
| uint8_t data = 0U; | ||
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| /* Read data from code stream. */ | ||
| if (false == readFromInStreamFunc(data)) | ||
| { | ||
| /* No more data is available, abort now. */ | ||
| isSuccessful = false; | ||
| } | ||
| else | ||
| { | ||
| m_codeBuffer = data; | ||
| m_bitsInBuffer = 8U; | ||
| } | ||
| } | ||
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| if (true == isSuccessful) | ||
| { | ||
| uint32_t bitsAvailable = (m_bitsInBuffer < codeBitsNeeded) ? m_bitsInBuffer : codeBitsNeeded; | ||
| uint32_t mask = (1U << bitsAvailable) - 1U; /* Mask for n bits. */ | ||
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| code |= (m_codeBuffer & mask) << (m_codeWidth - codeBitsNeeded); | ||
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| /* Remove bits from code buffer. */ | ||
| m_codeBuffer >>= bitsAvailable; | ||
| m_bitsInBuffer -= bitsAvailable; | ||
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| /* Now less bits are needed. */ | ||
| codeBitsNeeded -= bitsAvailable; | ||
| } | ||
| } | ||
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| return isSuccessful; | ||
| } | ||
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| bool LzwDecoder::decompress(uint32_t& code, WriteToOutStream writeToOutStreamFunc) | ||
| { | ||
| bool isSuccessful = true; | ||
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| if (true == m_isInitialState) | ||
| { | ||
| uint8_t data = code & 0xFFU; | ||
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| m_firstByte = code; | ||
| m_prevCode = code; | ||
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| /* Is code invalid? */ | ||
| if (code > m_endCode) | ||
| { | ||
| isSuccessful = false; | ||
| } | ||
| else if (false == writeToOutStreamFunc(data)) | ||
| { | ||
| isSuccessful = false; | ||
| } | ||
| else | ||
| { | ||
| m_isInitialState = false; | ||
| } | ||
| } | ||
| else | ||
| { | ||
| m_inCode = code; | ||
|
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| /* Handle the KwKwK case. */ | ||
| if (code >= m_nextCode) | ||
| { | ||
| /* Invalid data? */ | ||
| if (code != m_nextCode) | ||
| { | ||
| isSuccessful = false; | ||
| } | ||
| else | ||
| { | ||
| *m_stackPtr = m_firstByte & 0xFFU; | ||
| ++m_stackPtr; | ||
| code = m_prevCode; | ||
| } | ||
| } | ||
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| if (true == isSuccessful) | ||
| { | ||
| /* "Unwind" code's string to stack. */ | ||
| while(code >= m_clearCode) | ||
| { | ||
| /* Heads are packed to left of tails in codes. */ | ||
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| /* Tails */ | ||
| *m_stackPtr = m_codes[code] & 0xFFU; | ||
| ++m_stackPtr; | ||
|
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| /* Heads*/ | ||
| code = (m_codes[code] >> 8U) & 0x0FFFU; | ||
| } | ||
|
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| m_firstByte = code; | ||
| *m_stackPtr = code & 0xFFU; | ||
| ++m_stackPtr; | ||
|
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| do | ||
| { | ||
| --m_stackPtr; | ||
|
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| if (false == writeToOutStreamFunc(*m_stackPtr)) | ||
| { | ||
| isSuccessful = false; | ||
| } | ||
| } | ||
| while((m_stackPtr > m_stack) && (true == isSuccessful)); | ||
| } | ||
|
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| if (true == isSuccessful) | ||
| { | ||
| if (m_nextCode < CODE_LIMIT) | ||
| { | ||
| /* Heads are packed to left of tails in codes. */ | ||
| m_codes[m_nextCode] = (m_prevCode << 8U) | code; | ||
| ++m_nextCode; | ||
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| if ((m_nextCode > m_maxCode) && (m_nextCode < CODE_LIMIT)) | ||
| { | ||
| m_maxCode = m_maxCode * 2U + 1U; | ||
| ++m_codeWidth; | ||
| } | ||
| } | ||
|
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| m_prevCode = m_inCode; | ||
| } | ||
| } | ||
|
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| return isSuccessful; | ||
| } | ||
|
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| /****************************************************************************** | ||
| * External Functions | ||
| *****************************************************************************/ | ||
|
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| /****************************************************************************** | ||
| * Local Functions | ||
| *****************************************************************************/ |
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