From be9ac57b9d2e27697262489002ee9334d4db61d2 Mon Sep 17 00:00:00 2001 From: Lioncash Date: Thu, 15 Aug 2019 23:19:24 -0400 Subject: [PATCH] LZBase: Mark functions as const where applicable Most of the interface can be const qualified except for the setters. While we're at it, we can also make the private member functions internally linked helper functions, given they don't depend on instance state at all. --- include/LZ77/LZBase.hpp | 17 ++-- src/LZ77/LZBase.cpp | 180 ++++++++++++++++++++-------------------- 2 files changed, 97 insertions(+), 100 deletions(-) diff --git a/include/LZ77/LZBase.hpp b/include/LZ77/LZBase.hpp index 74d244e..b4d1c06 100644 --- a/include/LZ77/LZBase.hpp +++ b/include/LZ77/LZBase.hpp @@ -13,23 +13,18 @@ public: virtual atUint32 decompress(const atUint8* src, atUint8** dest, atUint32 srcLength) = 0; void setSlidingWindow(atInt32 SlidingWindow); - atInt32 slidingWindow(); + atInt32 slidingWindow() const; void setReadAheadBuffer(atInt32 ReadAheadBuffer); - atInt32 readAheadBuffer(); + atInt32 readAheadBuffer() const; void setMinMatch(atInt32 minimumMatch); - atInt32 minMatch(); + atInt32 minMatch() const; void setBlockSize(atInt32 BlockSize); - atInt32 blockSize(); + atInt32 blockSize() const; void setMinimumOffset(atUint32 minimumOffset); - atUint32 minimumOffset(); - -private: - atInt32 subMatch(const atUint8* str1, const uint8_t* str2, const atInt32 len); - LZLengthOffset windowSearch(atUint8* beginSearchPtr, atUint8* searchPosPtr, atUint8* endLABufferPtr, - atUint8* startLBPtr); + atUint32 minimumOffset() const; protected: - LZLengthOffset search(atUint8* posPtr, atUint8* dataBegin, atUint8* dataEnd); + LZLengthOffset search(const atUint8* posPtr, const atUint8* dataBegin, const atUint8* dataEnd) const; atInt32 m_slidingWindow; atInt32 m_readAheadBuffer; diff --git a/src/LZ77/LZBase.cpp b/src/LZ77/LZBase.cpp index c404f1c..461eb7e 100644 --- a/src/LZ77/LZBase.cpp +++ b/src/LZ77/LZBase.cpp @@ -1,75 +1,10 @@ #include "LZ77/LZLookupTable.hpp" #include "LZ77/LZBase.hpp" -LZBase::LZBase(atInt32 minimumOffset, atInt32 slidingWindow, atInt32 minimumMatch, atInt32 blockSize) -: m_slidingWindow(slidingWindow) -, m_readAheadBuffer(minimumMatch) -, m_minMatch(minimumMatch) -, m_blockSize(blockSize) -, m_minOffset(minimumOffset) {} - -void LZBase::setSlidingWindow(atInt32 slidingWindow) { m_slidingWindow = slidingWindow; } - -atInt32 LZBase::slidingWindow() { return m_slidingWindow; } - -void LZBase::setReadAheadBuffer(atInt32 readAheadBuffer) { m_readAheadBuffer = readAheadBuffer; } - -atInt32 LZBase::readAheadBuffer() { return m_readAheadBuffer; } - -void LZBase::setMinMatch(atInt32 minimumMatch) { m_minMatch = minimumMatch; } - -atInt32 LZBase::minMatch() { return m_minMatch; } - -void LZBase::setBlockSize(atInt32 blockSize) { m_blockSize = blockSize; } - -atInt32 LZBase::blockSize() { return m_blockSize; } - -void LZBase::setMinimumOffset(atUint32 minimumOffset) { m_minOffset = minimumOffset; } - -atUint32 LZBase::minimumOffset() { return m_minOffset; } - -/* - DerricMc: - This search function is my own work and is no way affilated with any one else - I use the my own window_search function to drastically speed up the search function - Normally a search for one byte is matched, then two, then three, all the way up - to the size of the LookAheadBuffer. So I decided to skip the incremental search - and search for the entire LookAheadBuffer and if I don't find the bytes are equal I return - the next best match(which means if I look for 18 bytes and they are not found 18 bytess did not match, - and 17 bytes did match then 17 bytes match is return). - -*/ -LZLengthOffset LZBase::search(atUint8* posPtr, atUint8* dataBegin, atUint8* dataEnd) { - LZLengthOffset results = {0, 0}; - - // Returns negative 1 for Search failures since the current position is passed the size to be compressed - if (posPtr >= dataEnd) { - results.length = -1; - return results; - } - - atUint8* searchWindow; - // LookAheadBuffer is ReadAheadBuffer Size if there are more bytes than ReadAheadBufferSize waiting - // to be compressed else the number of remaining bytes is the LookAheadBuffer - int lookAheadBuffer_len = ((int)(dataEnd - posPtr) < m_readAheadBuffer) ? (int)(dataEnd - posPtr) : m_readAheadBuffer; - int slidingBuffer = (int)(posPtr - dataBegin) - m_slidingWindow; - - if (slidingBuffer > 0) - searchWindow = dataBegin + slidingBuffer; - else - searchWindow = dataBegin; - - atUint8* endPos = posPtr + lookAheadBuffer_len; - - if (!((posPtr - dataBegin < 1) || (dataEnd - posPtr < m_minMatch))) - results = windowSearch(searchWindow, posPtr, endPos, posPtr - m_minOffset); - - return results; -} - +namespace { // Returns the full length of string2 if they are equal else // Return the number of characters that were equal before they weren't equal -int LZBase::subMatch(const uint8_t* str1, const uint8_t* str2, const int len) { +int subMatch(const uint8_t* str1, const uint8_t* str2, const int len) { for (int i = 0; i < len; ++i) if (str1[i] != str2[i]) return i; @@ -77,24 +12,22 @@ int LZBase::subMatch(const uint8_t* str1, const uint8_t* str2, const int len) { return len; } -/* -Normally a search for one byte is matched, then two, then three, all the way up - to the size of the LookAheadBuffer. So I decided to skip the incremental search - and search for the entire LookAheadBuffer and if the function doesn't find the bytes are - equal the function return the next best match(which means if the function look for 18 bytes and they are not found, -return the number of bytes that did match before it failed to match. The submatch is function returns the number of -bytes that were equal, which can result up to the bytes total length if both byte strings are equal. - - - ...[][][][][][][][][][][][]|[][][][][][][][][][][][][][] - | - Search Window Current Pos LookAheadBuffer - Up to 4096 bytes Up to 18 bytes - Sliding Window - Up to 4114 bytes -*/ -LZLengthOffset LZBase::windowSearch(atUint8* beginSearchPtr, atUint8* searchPosPtr, atUint8* endLABufferPtr, - atUint8* startLBPtr) { +// Normally a search for one byte is matched, then two, then three, all the way up +// to the size of the LookAheadBuffer. So I decided to skip the incremental search +// and search for the entire LookAheadBuffer and if the function doesn't find the bytes are +// equal the function return the next best match(which means if the function look for 18 bytes and they are not found, +// return the number of bytes that did match before it failed to match. The submatch is function returns the number of +// bytes that were equal, which can result up to the bytes total length if both byte strings are equal. +// +// +// ...[][][][][][][][][][][][]|[][][][][][][][][][][][][][] +// | +// Search Window Current Pos LookAheadBuffer +// Up to 4096 bytes Up to 18 bytes +// Sliding Window +// Up to 4114 bytes +LZLengthOffset windowSearch(const atUint8* beginSearchPtr, const atUint8* searchPosPtr, const atUint8* endLABufferPtr, + const atUint8* startLBPtr) { atInt32 size = (atUint32)(endLABufferPtr - beginSearchPtr); // Size of the entire sliding window atInt32 n = (atUint32)(endLABufferPtr - searchPosPtr); LZLengthOffset result = {0, 0}; @@ -103,10 +36,10 @@ LZLengthOffset LZBase::windowSearch(atUint8* beginSearchPtr, atUint8* searchPosP if (n > size) // If the string that is being looked for is bigger than the string that is being searched return result; - /*This makes sure that search for the searchPosPtr can be searched if an invalid position is given - An invalid position occurs if the amount of characters to search in_beginSearchPtr is less than the size - of searchPosPtr. In other words there has to be at least n characters left in the string - to have a chance to find n characters*/ + // This makes sure that search for the searchPosPtr can be searched if an invalid position is given + // An invalid position occurs if the amount of characters to search in_beginSearchPtr is less than the size + // of searchPosPtr. In other words there has to be at least n characters left in the string + // to have a chance to find n characters do { temp = subMatch(startLBPtr, searchPosPtr, n); @@ -125,3 +58,72 @@ LZLengthOffset LZBase::windowSearch(atUint8* beginSearchPtr, atUint8* searchPosP return result; } +} // Anonymous namespace + +LZBase::LZBase(atInt32 minimumOffset, atInt32 slidingWindow, atInt32 minimumMatch, atInt32 blockSize) +: m_slidingWindow(slidingWindow) +, m_readAheadBuffer(minimumMatch) +, m_minMatch(minimumMatch) +, m_blockSize(blockSize) +, m_minOffset(minimumOffset) {} + +void LZBase::setSlidingWindow(atInt32 slidingWindow) { m_slidingWindow = slidingWindow; } + +atInt32 LZBase::slidingWindow() const { return m_slidingWindow; } + +void LZBase::setReadAheadBuffer(atInt32 readAheadBuffer) { m_readAheadBuffer = readAheadBuffer; } + +atInt32 LZBase::readAheadBuffer() const { return m_readAheadBuffer; } + +void LZBase::setMinMatch(atInt32 minimumMatch) { m_minMatch = minimumMatch; } + +atInt32 LZBase::minMatch() const { return m_minMatch; } + +void LZBase::setBlockSize(atInt32 blockSize) { m_blockSize = blockSize; } + +atInt32 LZBase::blockSize() const { return m_blockSize; } + +void LZBase::setMinimumOffset(atUint32 minimumOffset) { m_minOffset = minimumOffset; } + +atUint32 LZBase::minimumOffset() const { return m_minOffset; } + +/* + DerricMc: + This search function is my own work and is no way affiliated with any one else + I use the my own window_search function to drastically speed up the search function + Normally a search for one byte is matched, then two, then three, all the way up + to the size of the LookAheadBuffer. So I decided to skip the incremental search + and search for the entire LookAheadBuffer and if I don't find the bytes are equal I return + the next best match(which means if I look for 18 bytes and they are not found 18 bytes did not match, + and 17 bytes did match then 17 bytes match is return). + +*/ +LZLengthOffset LZBase::search(const atUint8* posPtr, const atUint8* dataBegin, const atUint8* dataEnd) const { + LZLengthOffset results = {0, 0}; + + // Returns negative 1 for Search failures since the current position is passed the size to be compressed + if (posPtr >= dataEnd) { + results.length = -1; + return results; + } + + const atUint8* searchWindow; + // LookAheadBuffer is ReadAheadBuffer Size if there are more bytes than ReadAheadBufferSize waiting + // to be compressed else the number of remaining bytes is the LookAheadBuffer + const int lookAheadBuffer_len = + ((int)(dataEnd - posPtr) < m_readAheadBuffer) ? (int)(dataEnd - posPtr) : m_readAheadBuffer; + const int slidingBuffer = (int)(posPtr - dataBegin) - m_slidingWindow; + + if (slidingBuffer > 0) + searchWindow = dataBegin + slidingBuffer; + else + searchWindow = dataBegin; + + const atUint8* endPos = posPtr + lookAheadBuffer_len; + + if (!((posPtr - dataBegin < 1) || (dataEnd - posPtr < m_minMatch))) + results = windowSearch(searchWindow, posPtr, endPos, posPtr - m_minOffset); + + return results; +} +