mirror of
https://github.com/tursodatabase/libsql.git
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293 lines
9.4 KiB
C
293 lines
9.4 KiB
C
/*
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** 2022-11-18
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**
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** The author disclaims copyright to this source code. In place of
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** a legal notice, here is a blessing:
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**
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** May you do good and not evil.
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** May you find forgiveness for yourself and forgive others.
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** May you share freely, never taking more than you give.
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**
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*************************************************************************
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**
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** This is a SQLite extension for converting in either direction
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** between a (binary) blob and base64 text. Base64 can transit a
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** sane USASCII channel unmolested. It also plays nicely in CSV or
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** written as TCL brace-enclosed literals or SQL string literals,
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** and can be used unmodified in XML-like documents.
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**
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** This is an independent implementation of conversions specified in
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** RFC 4648, done on the above date by the author (Larry Brasfield)
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** who thereby has the right to put this into the public domain.
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**
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** The conversions meet RFC 4648 requirements, provided that this
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** C source specifies that line-feeds are included in the encoded
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** data to limit visible line lengths to 72 characters and to
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** terminate any encoded blob having non-zero length.
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**
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** Length limitations are not imposed except that the runtime
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** SQLite string or blob length limits are respected. Otherwise,
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** any length binary sequence can be represented and recovered.
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** Generated base64 sequences, with their line-feeds included,
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** can be concatenated; the result converted back to binary will
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** be the concatenation of the represented binary sequences.
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**
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** This SQLite3 extension creates a function, base64(x), which
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** either: converts text x containing base64 to a returned blob;
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** or converts a blob x to returned text containing base64. An
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** error will be thrown for other input argument types.
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**
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** This code relies on UTF-8 encoding only with respect to the
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** meaning of the first 128 (7-bit) codes matching that of USASCII.
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** It will fail miserably if somehow made to try to convert EBCDIC.
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** Because it is table-driven, it could be enhanced to handle that,
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** but the world and SQLite have moved on from that anachronism.
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**
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** To build the extension:
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** Set shell variable SQDIR=<your favorite SQLite checkout directory>
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** *Nix: gcc -O2 -shared -I$SQDIR -fPIC -o base64.so base64.c
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** OSX: gcc -O2 -dynamiclib -fPIC -I$SQDIR -o base64.dylib base64.c
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** Win32: gcc -O2 -shared -I%SQDIR% -o base64.dll base64.c
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** Win32: cl /Os -I%SQDIR% base64.c -link -dll -out:base64.dll
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*/
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#include <assert.h>
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#include "sqlite3ext.h"
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#ifndef deliberate_fall_through
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/* Quiet some compilers about some of our intentional code. */
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# if GCC_VERSION>=7000000
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# define deliberate_fall_through __attribute__((fallthrough));
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# else
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# define deliberate_fall_through
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# endif
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#endif
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SQLITE_EXTENSION_INIT1;
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#define PC 0x80 /* pad character */
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#define WS 0x81 /* whitespace */
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#define ND 0x82 /* Not above or digit-value */
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#define PAD_CHAR '='
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#ifndef U8_TYPEDEF
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typedef unsigned char u8;
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#define U8_TYPEDEF
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#endif
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/* Decoding table, ASCII (7-bit) value to base 64 digit value or other */
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static const u8 b64DigitValues[128] = {
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/* HT LF VT FF CR */
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ND,ND,ND,ND, ND,ND,ND,ND, ND,WS,WS,WS, WS,WS,ND,ND,
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/* US */
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ND,ND,ND,ND, ND,ND,ND,ND, ND,ND,ND,ND, ND,ND,ND,ND,
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/*sp + / */
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WS,ND,ND,ND, ND,ND,ND,ND, ND,ND,ND,62, ND,ND,ND,63,
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/* 0 1 5 9 = */
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52,53,54,55, 56,57,58,59, 60,61,ND,ND, ND,PC,ND,ND,
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/* A O */
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ND, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 11,12,13,14,
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/* P Z */
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15,16,17,18, 19,20,21,22, 23,24,25,ND, ND,ND,ND,ND,
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/* a o */
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ND,26,27,28, 29,30,31,32, 33,34,35,36, 37,38,39,40,
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/* p z */
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41,42,43,44, 45,46,47,48, 49,50,51,ND, ND,ND,ND,ND
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};
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static const char b64Numerals[64+1]
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= "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
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#define BX_DV_PROTO(c) \
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((((u8)(c))<0x80)? (u8)(b64DigitValues[(u8)(c)]) : 0x80)
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#define IS_BX_DIGIT(bdp) (((u8)(bdp))<0x80)
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#define IS_BX_WS(bdp) ((bdp)==WS)
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#define IS_BX_PAD(bdp) ((bdp)==PC)
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#define BX_NUMERAL(dv) (b64Numerals[(u8)(dv)])
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/* Width of base64 lines. Should be an integer multiple of 4. */
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#define B64_DARK_MAX 72
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/* Encode a byte buffer into base64 text with linefeeds appended to limit
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** encoded group lengths to B64_DARK_MAX or to terminate the last group.
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*/
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static char* toBase64( u8 *pIn, int nbIn, char *pOut ){
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int nCol = 0;
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while( nbIn >= 3 ){
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/* Do the bit-shuffle, exploiting unsigned input to avoid masking. */
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pOut[0] = BX_NUMERAL(pIn[0]>>2);
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pOut[1] = BX_NUMERAL(((pIn[0]<<4)|(pIn[1]>>4))&0x3f);
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pOut[2] = BX_NUMERAL(((pIn[1]&0xf)<<2)|(pIn[2]>>6));
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pOut[3] = BX_NUMERAL(pIn[2]&0x3f);
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pOut += 4;
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nbIn -= 3;
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pIn += 3;
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if( (nCol += 4)>=B64_DARK_MAX || nbIn<=0 ){
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*pOut++ = '\n';
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nCol = 0;
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}
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}
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if( nbIn > 0 ){
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signed char nco = nbIn+1;
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int nbe;
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unsigned long qv = *pIn++;
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for( nbe=1; nbe<3; ++nbe ){
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qv <<= 8;
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if( nbe<nbIn ) qv |= *pIn++;
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}
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for( nbe=3; nbe>=0; --nbe ){
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char ce = (nbe<nco)? BX_NUMERAL((u8)(qv & 0x3f)) : PAD_CHAR;
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qv >>= 6;
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pOut[nbe] = ce;
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}
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pOut += 4;
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*pOut++ = '\n';
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}
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*pOut = 0;
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return pOut;
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}
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/* Skip over text which is not base64 numeral(s). */
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static char * skipNonB64( char *s, int nc ){
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char c;
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while( nc-- > 0 && (c = *s) && !IS_BX_DIGIT(BX_DV_PROTO(c)) ) ++s;
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return s;
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}
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/* Decode base64 text into a byte buffer. */
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static u8* fromBase64( char *pIn, int ncIn, u8 *pOut ){
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if( ncIn>0 && pIn[ncIn-1]=='\n' ) --ncIn;
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while( ncIn>0 && *pIn!=PAD_CHAR ){
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static signed char nboi[] = { 0, 0, 1, 2, 3 };
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char *pUse = skipNonB64(pIn, ncIn);
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unsigned long qv = 0L;
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int nti, nbo, nac;
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ncIn -= (pUse - pIn);
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pIn = pUse;
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nti = (ncIn>4)? 4 : ncIn;
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ncIn -= nti;
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nbo = nboi[nti];
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if( nbo==0 ) break;
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for( nac=0; nac<4; ++nac ){
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char c = (nac<nti)? *pIn++ : b64Numerals[0];
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u8 bdp = BX_DV_PROTO(c);
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switch( bdp ){
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case ND:
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/* Treat dark non-digits as pad, but they terminate decode too. */
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ncIn = 0;
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deliberate_fall_through;
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case WS:
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/* Treat whitespace as pad and terminate this group.*/
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nti = nac;
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deliberate_fall_through;
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case PC:
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bdp = 0;
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--nbo;
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deliberate_fall_through;
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default: /* bdp is the digit value. */
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qv = qv<<6 | bdp;
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break;
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}
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}
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switch( nbo ){
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case 3:
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pOut[2] = (qv) & 0xff;
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case 2:
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pOut[1] = (qv>>8) & 0xff;
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case 1:
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pOut[0] = (qv>>16) & 0xff;
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}
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pOut += nbo;
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}
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return pOut;
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}
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/* This function does the work for the SQLite base64(x) UDF. */
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static void base64(sqlite3_context *context, int na, sqlite3_value *av[]){
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int nb, nc, nv = sqlite3_value_bytes(av[0]);
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int nvMax = sqlite3_limit(sqlite3_context_db_handle(context),
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SQLITE_LIMIT_LENGTH, -1);
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char *cBuf;
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u8 *bBuf;
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assert(na==1);
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switch( sqlite3_value_type(av[0]) ){
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case SQLITE_BLOB:
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nb = nv;
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nc = 4*(nv+2/3); /* quads needed */
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nc += (nc+(B64_DARK_MAX-1))/B64_DARK_MAX + 1; /* LFs and a 0-terminator */
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if( nvMax < nc ){
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sqlite3_result_error(context, "blob expanded to base64 too big", -1);
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return;
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}
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bBuf = (u8*)sqlite3_value_blob(av[0]);
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if( !bBuf ){
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if( SQLITE_NOMEM==sqlite3_errcode(sqlite3_context_db_handle(context)) ){
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goto memFail;
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}
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sqlite3_result_text(context,"",-1,SQLITE_STATIC);
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break;
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}
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cBuf = sqlite3_malloc(nc);
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if( !cBuf ) goto memFail;
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nc = (int)(toBase64(bBuf, nb, cBuf) - cBuf);
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sqlite3_result_text(context, cBuf, nc, sqlite3_free);
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break;
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case SQLITE_TEXT:
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nc = nv;
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nb = 3*((nv+3)/4); /* may overestimate due to LF and padding */
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if( nvMax < nb ){
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sqlite3_result_error(context, "blob from base64 may be too big", -1);
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return;
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}else if( nb<1 ){
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nb = 1;
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}
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cBuf = (char *)sqlite3_value_text(av[0]);
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if( !cBuf ){
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if( SQLITE_NOMEM==sqlite3_errcode(sqlite3_context_db_handle(context)) ){
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goto memFail;
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}
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sqlite3_result_zeroblob(context, 0);
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break;
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}
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bBuf = sqlite3_malloc(nb);
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if( !bBuf ) goto memFail;
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nb = (int)(fromBase64(cBuf, nc, bBuf) - bBuf);
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sqlite3_result_blob(context, bBuf, nb, sqlite3_free);
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break;
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default:
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sqlite3_result_error(context, "base64 accepts only blob or text", -1);
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return;
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}
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return;
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memFail:
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sqlite3_result_error(context, "base64 OOM", -1);
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}
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/*
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** Establish linkage to running SQLite library.
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*/
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#ifndef SQLITE_SHELL_EXTFUNCS
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#ifdef _WIN32
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__declspec(dllexport)
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#endif
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int sqlite3_base_init
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#else
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static int sqlite3_base64_init
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#endif
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(sqlite3 *db, char **pzErr, const sqlite3_api_routines *pApi){
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SQLITE_EXTENSION_INIT2(pApi);
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(void)pzErr;
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return sqlite3_create_function
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(db, "base64", 1,
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SQLITE_DETERMINISTIC|SQLITE_INNOCUOUS|SQLITE_DIRECTONLY|SQLITE_UTF8,
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0, base64, 0, 0);
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}
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/*
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** Define some macros to allow this extension to be built into the shell
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** conveniently, in conjunction with use of SQLITE_SHELL_EXTFUNCS. This
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** allows shell.c, as distributed, to have this extension built in.
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*/
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#define BASE64_INIT(db) sqlite3_base64_init(db, 0, 0)
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#define BASE64_EXPOSE(db, pzErr) /* Not needed, ..._init() does this. */
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