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-rw-r--r--src/serialize.h290
1 files changed, 237 insertions, 53 deletions
diff --git a/src/serialize.h b/src/serialize.h
index abc4f04a0d..9e14666fac 100644
--- a/src/serialize.h
+++ b/src/serialize.h
@@ -238,12 +238,77 @@ uint64 ReadCompactSize(Stream& is)
return nSizeRet;
}
+// Variable-length integers: bytes are a MSB base-128 encoding of the number.
+// The high bit in each byte signifies whether another digit follows. To make
+// the encoding is one-to-one, one is subtracted from all but the last digit.
+// Thus, the byte sequence a[] with length len, where all but the last byte
+// has bit 128 set, encodes the number:
+//
+// (a[len-1] & 0x7F) + sum(i=1..len-1, 128^i*((a[len-i-1] & 0x7F)+1))
+//
+// Properties:
+// * Very small (0-127: 1 byte, 128-16511: 2 bytes, 16512-2113663: 3 bytes)
+// * Every integer has exactly one encoding
+// * Encoding does not depend on size of original integer type
+// * No redundancy: every (infinite) byte sequence corresponds to a list
+// of encoded integers.
+//
+// 0: [0x00] 256: [0x81 0x00]
+// 1: [0x01] 16383: [0xFE 0x7F]
+// 127: [0x7F] 16384: [0xFF 0x00]
+// 128: [0x80 0x00] 16511: [0x80 0xFF 0x7F]
+// 255: [0x80 0x7F] 65535: [0x82 0xFD 0x7F]
+// 2^32: [0x8E 0xFE 0xFE 0xFF 0x00]
+
+template<typename I>
+inline unsigned int GetSizeOfVarInt(I n)
+{
+ int nRet = 0;
+ while(true) {
+ nRet++;
+ if (n <= 0x7F)
+ break;
+ n = (n >> 7) - 1;
+ }
+ return nRet;
+}
+template<typename Stream, typename I>
+void WriteVarInt(Stream& os, I n)
+{
+ unsigned char tmp[(sizeof(n)*8+6)/7];
+ int len=0;
+ while(true) {
+ tmp[len] = (n & 0x7F) | (len ? 0x80 : 0x00);
+ if (n <= 0x7F)
+ break;
+ n = (n >> 7) - 1;
+ len++;
+ }
+ do {
+ WRITEDATA(os, tmp[len]);
+ } while(len--);
+}
-#define FLATDATA(obj) REF(CFlatData((char*)&(obj), (char*)&(obj) + sizeof(obj)))
+template<typename Stream, typename I>
+I ReadVarInt(Stream& is)
+{
+ I n = 0;
+ while(true) {
+ unsigned char chData;
+ READDATA(is, chData);
+ n = (n << 7) | (chData & 0x7F);
+ if (chData & 0x80)
+ n++;
+ else
+ return n;
+ }
+}
+
+#define FLATDATA(obj) REF(CFlatData((char*)&(obj), (char*)&(obj) + sizeof(obj)))
+#define VARINT(obj) REF(WrapVarInt(REF(obj)))
/** Wrapper for serializing arrays and POD.
- * There's a clever template way to make arrays serialize normally, but MSVC6 doesn't support it.
*/
class CFlatData
{
@@ -275,6 +340,32 @@ public:
}
};
+template<typename I>
+class CVarInt
+{
+protected:
+ I &n;
+public:
+ CVarInt(I& nIn) : n(nIn) { }
+
+ unsigned int GetSerializeSize(int, int) const {
+ return GetSizeOfVarInt<I>(n);
+ }
+
+ template<typename Stream>
+ void Serialize(Stream &s, int, int) const {
+ WriteVarInt<Stream,I>(s, n);
+ }
+
+ template<typename Stream>
+ void Unserialize(Stream& s, int, int) {
+ n = ReadVarInt<Stream,I>(s);
+ }
+};
+
+template<typename I>
+CVarInt<I> WrapVarInt(I& n) { return CVarInt<I>(n); }
+
//
// Forward declarations
//
@@ -1010,57 +1101,6 @@ public:
}
};
-#ifdef TESTCDATASTREAM
-// VC6sp6
-// CDataStream:
-// n=1000 0 seconds
-// n=2000 0 seconds
-// n=4000 0 seconds
-// n=8000 0 seconds
-// n=16000 0 seconds
-// n=32000 0 seconds
-// n=64000 1 seconds
-// n=128000 1 seconds
-// n=256000 2 seconds
-// n=512000 4 seconds
-// n=1024000 8 seconds
-// n=2048000 16 seconds
-// n=4096000 32 seconds
-// stringstream:
-// n=1000 1 seconds
-// n=2000 1 seconds
-// n=4000 13 seconds
-// n=8000 87 seconds
-// n=16000 400 seconds
-// n=32000 1660 seconds
-// n=64000 6749 seconds
-// n=128000 27241 seconds
-// n=256000 109804 seconds
-#include <iostream>
-int main(int argc, char *argv[])
-{
- vector<unsigned char> vch(0xcc, 250);
- printf("CDataStream:\n");
- for (int n = 1000; n <= 4500000; n *= 2)
- {
- CDataStream ss;
- time_t nStart = time(NULL);
- for (int i = 0; i < n; i++)
- ss.write((char*)&vch[0], vch.size());
- printf("n=%-10d %d seconds\n", n, time(NULL) - nStart);
- }
- printf("stringstream:\n");
- for (int n = 1000; n <= 4500000; n *= 2)
- {
- stringstream ss;
- time_t nStart = time(NULL);
- for (int i = 0; i < n; i++)
- ss.write((char*)&vch[0], vch.size());
- printf("n=%-10d %d seconds\n", n, time(NULL) - nStart);
- }
-}
-#endif
-
@@ -1185,4 +1225,148 @@ public:
}
};
+/** Wrapper around a FILE* that implements a ring buffer to
+ * deserialize from. It guarantees the ability to rewind
+ * a given number of bytes. */
+class CBufferedFile
+{
+private:
+ FILE *src; // source file
+ uint64 nSrcPos; // how many bytes have been read from source
+ uint64 nReadPos; // how many bytes have been read from this
+ uint64 nReadLimit; // up to which position we're allowed to read
+ uint64 nRewind; // how many bytes we guarantee to rewind
+ std::vector<char> vchBuf; // the buffer
+
+ short state;
+ short exceptmask;
+
+protected:
+ void setstate(short bits, const char *psz) {
+ state |= bits;
+ if (state & exceptmask)
+ throw std::ios_base::failure(psz);
+ }
+
+ // read data from the source to fill the buffer
+ bool Fill() {
+ unsigned int pos = nSrcPos % vchBuf.size();
+ unsigned int readNow = vchBuf.size() - pos;
+ unsigned int nAvail = vchBuf.size() - (nSrcPos - nReadPos) - nRewind;
+ if (nAvail < readNow)
+ readNow = nAvail;
+ if (readNow == 0)
+ return false;
+ size_t read = fread((void*)&vchBuf[pos], 1, readNow, src);
+ if (read == 0) {
+ setstate(std::ios_base::failbit, feof(src) ? "CBufferedFile::Fill : end of file" : "CBufferedFile::Fill : fread failed");
+ return false;
+ } else {
+ nSrcPos += read;
+ return true;
+ }
+ }
+
+public:
+ int nType;
+ int nVersion;
+
+ CBufferedFile(FILE *fileIn, uint64 nBufSize, uint64 nRewindIn, int nTypeIn, int nVersionIn) :
+ src(fileIn), nSrcPos(0), nReadPos(0), nReadLimit((uint64)(-1)), nRewind(nRewindIn), vchBuf(nBufSize, 0),
+ state(0), exceptmask(std::ios_base::badbit | std::ios_base::failbit), nType(nTypeIn), nVersion(nVersionIn) {
+ }
+
+ // check whether no error occurred
+ bool good() const {
+ return state == 0;
+ }
+
+ // check whether we're at the end of the source file
+ bool eof() const {
+ return nReadPos == nSrcPos && feof(src);
+ }
+
+ // read a number of bytes
+ CBufferedFile& read(char *pch, size_t nSize) {
+ if (nSize + nReadPos > nReadLimit)
+ throw std::ios_base::failure("Read attempted past buffer limit");
+ if (nSize + nRewind > vchBuf.size())
+ throw std::ios_base::failure("Read larger than buffer size");
+ while (nSize > 0) {
+ if (nReadPos == nSrcPos)
+ Fill();
+ unsigned int pos = nReadPos % vchBuf.size();
+ size_t nNow = nSize;
+ if (nNow + pos > vchBuf.size())
+ nNow = vchBuf.size() - pos;
+ if (nNow + nReadPos > nSrcPos)
+ nNow = nSrcPos - nReadPos;
+ memcpy(pch, &vchBuf[pos], nNow);
+ nReadPos += nNow;
+ pch += nNow;
+ nSize -= nNow;
+ }
+ return (*this);
+ }
+
+ // return the current reading position
+ uint64 GetPos() {
+ return nReadPos;
+ }
+
+ // rewind to a given reading position
+ bool SetPos(uint64 nPos) {
+ nReadPos = nPos;
+ if (nReadPos + nRewind < nSrcPos) {
+ nReadPos = nSrcPos - nRewind;
+ return false;
+ } else if (nReadPos > nSrcPos) {
+ nReadPos = nSrcPos;
+ return false;
+ } else {
+ return true;
+ }
+ }
+
+ bool Seek(uint64 nPos) {
+ long nLongPos = nPos;
+ if (nPos != (uint64)nLongPos)
+ return false;
+ if (fseek(src, nLongPos, SEEK_SET))
+ return false;
+ nLongPos = ftell(src);
+ nSrcPos = nLongPos;
+ nReadPos = nLongPos;
+ state = 0;
+ return true;
+ }
+
+ // prevent reading beyond a certain position
+ // no argument removes the limit
+ bool SetLimit(uint64 nPos = (uint64)(-1)) {
+ if (nPos < nReadPos)
+ return false;
+ nReadLimit = nPos;
+ return true;
+ }
+
+ template<typename T>
+ CBufferedFile& operator>>(T& obj) {
+ // Unserialize from this stream
+ ::Unserialize(*this, obj, nType, nVersion);
+ return (*this);
+ }
+
+ // search for a given byte in the stream, and remain positioned on it
+ void FindByte(char ch) {
+ while (true) {
+ if (nReadPos == nSrcPos)
+ Fill();
+ if (vchBuf[nReadPos % vchBuf.size()] == ch)
+ break;
+ nReadPos++;
+ }
+ }
+};
+
#endif
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