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Diffstat (limited to 'ext/sqlite/libsqlite/src/encode.c')
| -rw-r--r-- | ext/sqlite/libsqlite/src/encode.c | 165 |
1 files changed, 165 insertions, 0 deletions
diff --git a/ext/sqlite/libsqlite/src/encode.c b/ext/sqlite/libsqlite/src/encode.c new file mode 100644 index 0000000000..6ad100ce5b --- /dev/null +++ b/ext/sqlite/libsqlite/src/encode.c @@ -0,0 +1,165 @@ +/* +** 2002 April 25 +** +** The author disclaims copyright to this source code. In place of +** a legal notice, here is a blessing: +** +** May you do good and not evil. +** May you find forgiveness for yourself and forgive others. +** May you share freely, never taking more than you give. +** +************************************************************************* +** This file contains helper routines used to translate binary data into +** a null-terminated string (suitable for use in SQLite) and back again. +** These are convenience routines for use by people who want to store binary +** data in an SQLite database. The code in this file is not used by any other +** part of the SQLite library. +** +** $Id$ +*/ +#include <string.h> + +/* +** Encode a binary buffer "in" of size n bytes so that it contains +** no instances of characters '\'' or '\000'. The output is +** null-terminated and can be used as a string value in an INSERT +** or UPDATE statement. Use sqlite_decode_binary() to convert the +** string back into its original binary. +** +** The result is written into a preallocated output buffer "out". +** "out" must be able to hold at least (256*n + 1262)/253 bytes. +** In other words, the output will be expanded by as much as 3 +** bytes for every 253 bytes of input plus 2 bytes of fixed overhead. +** (This is approximately 2 + 1.019*n or about a 2% size increase.) +** +** The return value is the number of characters in the encoded +** string, excluding the "\000" terminator. +*/ +int sqlite_encode_binary(const unsigned char *in, int n, unsigned char *out){ + int i, j, e, m; + int cnt[256]; + if( n<=0 ){ + out[0] = 'x'; + out[1] = 0; + return 1; + } + memset(cnt, 0, sizeof(cnt)); + for(i=n-1; i>=0; i--){ cnt[in[i]]++; } + m = n; + for(i=1; i<256; i++){ + int sum; + if( i=='\'' ) continue; + sum = cnt[i] + cnt[(i+1)&0xff] + cnt[(i+'\'')&0xff]; + if( sum<m ){ + m = sum; + e = i; + if( m==0 ) break; + } + } + out[0] = e; + j = 1; + for(i=0; i<n; i++){ + int c = (in[i] - e)&0xff; + if( c==0 ){ + out[j++] = 1; + out[j++] = 1; + }else if( c==1 ){ + out[j++] = 1; + out[j++] = 2; + }else if( c=='\'' ){ + out[j++] = 1; + out[j++] = 3; + }else{ + out[j++] = c; + } + } + out[j] = 0; + return j; +} + +/* +** Decode the string "in" into binary data and write it into "out". +** This routine reverses the encoded created by sqlite_encode_binary(). +** The output will always be a few bytes less than the input. The number +** of bytes of output is returned. If the input is not a well-formed +** encoding, -1 is returned. +** +** The "in" and "out" parameters may point to the same buffer in order +** to decode a string in place. +*/ +int sqlite_decode_binary(const unsigned char *in, unsigned char *out){ + int i, c, e; + e = *(in++); + i = 0; + while( (c = *(in++))!=0 ){ + if( c==1 ){ + c = *(in++); + if( c==1 ){ + c = 0; + }else if( c==2 ){ + c = 1; + }else if( c==3 ){ + c = '\''; + }else{ + return -1; + } + } + out[i++] = (c + e)&0xff; + } + return i; +} + +#ifdef ENCODER_TEST +/* +** The subroutines above are not tested by the usual test suite. To test +** these routines, compile just this one file with a -DENCODER_TEST=1 option +** and run the result. +*/ +int main(int argc, char **argv){ + int i, j, n, m, nOut; + unsigned char in[30000]; + unsigned char out[33000]; + + for(i=0; i<sizeof(in); i++){ + printf("Test %d: ", i+1); + n = rand() % (i+1); + if( i%100==0 ){ + int k; + for(j=k=0; j<n; j++){ + /* if( k==0 || k=='\'' ) k++; */ + in[j] = k; + k = (k+1)&0xff; + } + }else{ + for(j=0; j<n; j++) in[j] = rand() & 0xff; + } + nOut = sqlite_encode_binary(in, n, out); + if( nOut!=strlen(out) ){ + printf(" ERROR return value is %d instead of %d\n", nOut, strlen(out)); + exit(1); + } + m = (256*n + 1262)/253; + printf("size %d->%d (max %d)", n, strlen(out)+1, m); + if( strlen(out)+1>m ){ + printf(" ERROR output too big\n"); + exit(1); + } + for(j=0; out[j]; j++){ + if( out[j]=='\'' ){ + printf(" ERROR contains (')\n"); + exit(1); + } + } + j = sqlite_decode_binary(out, out); + if( j!=n ){ + printf(" ERROR decode size %d\n", j); + exit(1); + } + if( memcmp(in, out, n)!=0 ){ + printf(" ERROR decode mismatch\n"); + exit(1); + } + printf(" OK\n"); + } +} +#endif /* ENCODER_TEST */ |