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sqlite/ext/misc/fossildelta.c
drh 1935887a68 Ensure that all fields of static sqlite3_module objects are explicitly 
initialized, in order to hush-up nuisance compiler warnings.

FossilOrigin-Name: f3b3d712d6e58b1cb8fdebd2b6b3125080b6b3ac8c7c849a8cc1e5e778d62fe7
2023-10-06 12:51:05 +00:00

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/*
** 2019-02-19
**
** 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 SQLite extension implements the delta functions used by the RBU
** extension. Three scalar functions and one table-valued function are
** implemented here:
**
** delta_apply(X,D) -- apply delta D to file X and return the result
** delta_create(X,Y) -- compute and return a delta that carries X into Y
** delta_output_size(D) -- blob size in bytes output from applying delta D
** delta_parse(D) -- returns rows describing delta D
**
** The delta format is the Fossil delta format, described in a comment
** on the delete_create() function implementation below, and also at
**
** https://www.fossil-scm.org/fossil/doc/trunk/www/delta_format.wiki
**
** This delta format is used by the RBU extension, which is the main
** reason that these routines are included in the extension library.
** RBU does not use this extension directly. Rather, this extension is
** provided as a convenience to developers who want to analyze RBU files
** that contain deltas.
*/
#include <string.h>
#include <assert.h>
#include <stdlib.h>
#include "sqlite3ext.h"
SQLITE_EXTENSION_INIT1
#ifndef SQLITE_AMALGAMATION
/*
** The "u32" type must be an unsigned 32-bit integer. Adjust this
*/
typedef unsigned int u32;
/*
** Must be a 16-bit value
*/
typedef short int s16;
typedef unsigned short int u16;
#endif /* SQLITE_AMALGAMATION */
/*
** The width of a hash window in bytes. The algorithm only works if this
** is a power of 2.
*/
#define NHASH 16
/*
** The current state of the rolling hash.
**
** z[] holds the values that have been hashed. z[] is a circular buffer.
** z[i] is the first entry and z[(i+NHASH-1)%NHASH] is the last entry of
** the window.
**
** Hash.a is the sum of all elements of hash.z[]. Hash.b is a weighted
** sum. Hash.b is z[i]*NHASH + z[i+1]*(NHASH-1) + ... + z[i+NHASH-1]*1.
** (Each index for z[] should be module NHASH, of course. The %NHASH operator
** is omitted in the prior expression for brevity.)
*/
typedef struct hash hash;
struct hash {
u16 a, b; /* Hash values */
u16 i; /* Start of the hash window */
char z[NHASH]; /* The values that have been hashed */
};
/*
** Initialize the rolling hash using the first NHASH characters of z[]
*/
static void hash_init(hash *pHash, const char *z){
u16 a, b, i;
a = b = z[0];
for(i=1; i<NHASH; i++){
a += z[i];
b += a;
}
memcpy(pHash->z, z, NHASH);
pHash->a = a & 0xffff;
pHash->b = b & 0xffff;
pHash->i = 0;
}
/*
** Advance the rolling hash by a single character "c"
*/
static void hash_next(hash *pHash, int c){
u16 old = pHash->z[pHash->i];
pHash->z[pHash->i] = c;
pHash->i = (pHash->i+1)&(NHASH-1);
pHash->a = pHash->a - old + c;
pHash->b = pHash->b - NHASH*old + pHash->a;
}
/*
** Return a 32-bit hash value
*/
static u32 hash_32bit(hash *pHash){
return (pHash->a & 0xffff) | (((u32)(pHash->b & 0xffff))<<16);
}
/*
** Compute a hash on NHASH bytes.
**
** This routine is intended to be equivalent to:
** hash h;
** hash_init(&h, zInput);
** return hash_32bit(&h);
*/
static u32 hash_once(const char *z){
u16 a, b, i;
a = b = z[0];
for(i=1; i<NHASH; i++){
a += z[i];
b += a;
}
return a | (((u32)b)<<16);
}
/*
** Write an base-64 integer into the given buffer.
*/
static void putInt(unsigned int v, char **pz){
static const char zDigits[] =
"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz~";
/* 123456789 123456789 123456789 123456789 123456789 123456789 123 */
int i, j;
char zBuf[20];
if( v==0 ){
*(*pz)++ = '0';
return;
}
for(i=0; v>0; i++, v>>=6){
zBuf[i] = zDigits[v&0x3f];
}
for(j=i-1; j>=0; j--){
*(*pz)++ = zBuf[j];
}
}
/*
** Read bytes from *pz and convert them into a positive integer. When
** finished, leave *pz pointing to the first character past the end of
** the integer. The *pLen parameter holds the length of the string
** in *pz and is decremented once for each character in the integer.
*/
static unsigned int deltaGetInt(const char **pz, int *pLen){
static const signed char zValue[] = {
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -1, -1, -1, -1, -1, -1,
-1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, -1, -1, -1, -1, 36,
-1, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51,
52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, -1, -1, -1, 63, -1,
};
unsigned int v = 0;
int c;
unsigned char *z = (unsigned char*)*pz;
unsigned char *zStart = z;
while( (c = zValue[0x7f&*(z++)])>=0 ){
v = (v<<6) + c;
}
z--;
*pLen -= z - zStart;
*pz = (char*)z;
return v;
}
/*
** Return the number digits in the base-64 representation of a positive integer
*/
static int digit_count(int v){
unsigned int i, x;
for(i=1, x=64; v>=x; i++, x <<= 6){}
return i;
}
#ifdef __GNUC__
# define GCC_VERSION (__GNUC__*1000000+__GNUC_MINOR__*1000+__GNUC_PATCHLEVEL__)
#else
# define GCC_VERSION 0
#endif
/*
** Compute a 32-bit big-endian checksum on the N-byte buffer. If the
** buffer is not a multiple of 4 bytes length, compute the sum that would
** have occurred if the buffer was padded with zeros to the next multiple
** of four bytes.
*/
static unsigned int checksum(const char *zIn, size_t N){
static const int byteOrderTest = 1;
const unsigned char *z = (const unsigned char *)zIn;
const unsigned char *zEnd = (const unsigned char*)&zIn[N&~3];
unsigned sum = 0;
assert( (z - (const unsigned char*)0)%4==0 ); /* Four-byte alignment */
if( 0==*(char*)&byteOrderTest ){
/* This is a big-endian machine */
while( z<zEnd ){
sum += *(unsigned*)z;
z += 4;
}
}else{
/* A little-endian machine */
#if GCC_VERSION>=4003000
while( z<zEnd ){
sum += __builtin_bswap32(*(unsigned*)z);
z += 4;
}
#elif defined(_MSC_VER) && _MSC_VER>=1300
while( z<zEnd ){
sum += _byteswap_ulong(*(unsigned*)z);
z += 4;
}
#else
unsigned sum0 = 0;
unsigned sum1 = 0;
unsigned sum2 = 0;
while(N >= 16){
sum0 += ((unsigned)z[0] + z[4] + z[8] + z[12]);
sum1 += ((unsigned)z[1] + z[5] + z[9] + z[13]);
sum2 += ((unsigned)z[2] + z[6] + z[10]+ z[14]);
sum += ((unsigned)z[3] + z[7] + z[11]+ z[15]);
z += 16;
N -= 16;
}
while(N >= 4){
sum0 += z[0];
sum1 += z[1];
sum2 += z[2];
sum += z[3];
z += 4;
N -= 4;
}
sum += (sum2 << 8) + (sum1 << 16) + (sum0 << 24);
#endif
}
switch(N&3){
case 3: sum += (z[2] << 8);
case 2: sum += (z[1] << 16);
case 1: sum += (z[0] << 24);
default: ;
}
return sum;
}
/*
** Create a new delta.
**
** The delta is written into a preallocated buffer, zDelta, which
** should be at least 60 bytes longer than the target file, zOut.
** The delta string will be NUL-terminated, but it might also contain
** embedded NUL characters if either the zSrc or zOut files are
** binary. This function returns the length of the delta string
** in bytes, excluding the final NUL terminator character.
**
** Output Format:
**
** The delta begins with a base64 number followed by a newline. This
** number is the number of bytes in the TARGET file. Thus, given a
** delta file z, a program can compute the size of the output file
** simply by reading the first line and decoding the base-64 number
** found there. The delta_output_size() routine does exactly this.
**
** After the initial size number, the delta consists of a series of
** literal text segments and commands to copy from the SOURCE file.
** A copy command looks like this:
**
** NNN@MMM,
**
** where NNN is the number of bytes to be copied and MMM is the offset
** into the source file of the first byte (both base-64). If NNN is 0
** it means copy the rest of the input file. Literal text is like this:
**
** NNN:TTTTT
**
** where NNN is the number of bytes of text (base-64) and TTTTT is the text.
**
** The last term is of the form
**
** NNN;
**
** In this case, NNN is a 32-bit bigendian checksum of the output file
** that can be used to verify that the delta applied correctly. All
** numbers are in base-64.
**
** Pure text files generate a pure text delta. Binary files generate a
** delta that may contain some binary data.
**
** Algorithm:
**
** The encoder first builds a hash table to help it find matching
** patterns in the source file. 16-byte chunks of the source file
** sampled at evenly spaced intervals are used to populate the hash
** table.
**
** Next we begin scanning the target file using a sliding 16-byte
** window. The hash of the 16-byte window in the target is used to
** search for a matching section in the source file. When a match
** is found, a copy command is added to the delta. An effort is
** made to extend the matching section to regions that come before
** and after the 16-byte hash window. A copy command is only issued
** if the result would use less space that just quoting the text
** literally. Literal text is added to the delta for sections that
** do not match or which can not be encoded efficiently using copy
** commands.
*/
static int delta_create(
const char *zSrc, /* The source or pattern file */
unsigned int lenSrc, /* Length of the source file */
const char *zOut, /* The target file */
unsigned int lenOut, /* Length of the target file */
char *zDelta /* Write the delta into this buffer */
){
int i, base;
char *zOrigDelta = zDelta;
hash h;
int nHash; /* Number of hash table entries */
int *landmark; /* Primary hash table */
int *collide; /* Collision chain */
int lastRead = -1; /* Last byte of zSrc read by a COPY command */
/* Add the target file size to the beginning of the delta
*/
putInt(lenOut, &zDelta);
*(zDelta++) = '\n';
/* If the source file is very small, it means that we have no
** chance of ever doing a copy command. Just output a single
** literal segment for the entire target and exit.
*/
if( lenSrc<=NHASH ){
putInt(lenOut, &zDelta);
*(zDelta++) = ':';
memcpy(zDelta, zOut, lenOut);
zDelta += lenOut;
putInt(checksum(zOut, lenOut), &zDelta);
*(zDelta++) = ';';
return zDelta - zOrigDelta;
}
/* Compute the hash table used to locate matching sections in the
** source file.
*/
nHash = lenSrc/NHASH;
collide = sqlite3_malloc64( (sqlite3_int64)nHash*2*sizeof(int) );
memset(collide, -1, nHash*2*sizeof(int));
landmark = &collide[nHash];
for(i=0; i<lenSrc-NHASH; i+=NHASH){
int hv = hash_once(&zSrc[i]) % nHash;
collide[i/NHASH] = landmark[hv];
landmark[hv] = i/NHASH;
}
/* Begin scanning the target file and generating copy commands and
** literal sections of the delta.
*/
base = 0; /* We have already generated everything before zOut[base] */
while( base+NHASH<lenOut ){
int iSrc, iBlock;
unsigned int bestCnt, bestOfst=0, bestLitsz=0;
hash_init(&h, &zOut[base]);
i = 0; /* Trying to match a landmark against zOut[base+i] */
bestCnt = 0;
while( 1 ){
int hv;
int limit = 250;
hv = hash_32bit(&h) % nHash;
iBlock = landmark[hv];
while( iBlock>=0 && (limit--)>0 ){
/*
** The hash window has identified a potential match against
** landmark block iBlock. But we need to investigate further.
**
** Look for a region in zOut that matches zSrc. Anchor the search
** at zSrc[iSrc] and zOut[base+i]. Do not include anything prior to
** zOut[base] or after zOut[outLen] nor anything after zSrc[srcLen].
**
** Set cnt equal to the length of the match and set ofst so that
** zSrc[ofst] is the first element of the match. litsz is the number
** of characters between zOut[base] and the beginning of the match.
** sz will be the overhead (in bytes) needed to encode the copy
** command. Only generate copy command if the overhead of the
** copy command is less than the amount of literal text to be copied.
*/
int cnt, ofst, litsz;
int j, k, x, y;
int sz;
int limitX;
/* Beginning at iSrc, match forwards as far as we can. j counts
** the number of characters that match */
iSrc = iBlock*NHASH;
y = base+i;
limitX = ( lenSrc-iSrc <= lenOut-y ) ? lenSrc : iSrc + lenOut - y;
for(x=iSrc; x<limitX; x++, y++){
if( zSrc[x]!=zOut[y] ) break;
}
j = x - iSrc - 1;
/* Beginning at iSrc-1, match backwards as far as we can. k counts
** the number of characters that match */
for(k=1; k<iSrc && k<=i; k++){
if( zSrc[iSrc-k]!=zOut[base+i-k] ) break;
}
k--;
/* Compute the offset and size of the matching region */
ofst = iSrc-k;
cnt = j+k+1;
litsz = i-k; /* Number of bytes of literal text before the copy */
/* sz will hold the number of bytes needed to encode the "insert"
** command and the copy command, not counting the "insert" text */
sz = digit_count(i-k)+digit_count(cnt)+digit_count(ofst)+3;
if( cnt>=sz && cnt>bestCnt ){
/* Remember this match only if it is the best so far and it
** does not increase the file size */
bestCnt = cnt;
bestOfst = iSrc-k;
bestLitsz = litsz;
}
/* Check the next matching block */
iBlock = collide[iBlock];
}
/* We have a copy command that does not cause the delta to be larger
** than a literal insert. So add the copy command to the delta.
*/
if( bestCnt>0 ){
if( bestLitsz>0 ){
/* Add an insert command before the copy */
putInt(bestLitsz,&zDelta);
*(zDelta++) = ':';
memcpy(zDelta, &zOut[base], bestLitsz);
zDelta += bestLitsz;
base += bestLitsz;
}
base += bestCnt;
putInt(bestCnt, &zDelta);
*(zDelta++) = '@';
putInt(bestOfst, &zDelta);
*(zDelta++) = ',';
if( bestOfst + bestCnt -1 > lastRead ){
lastRead = bestOfst + bestCnt - 1;
}
bestCnt = 0;
break;
}
/* If we reach this point, it means no match is found so far */
if( base+i+NHASH>=lenOut ){
/* We have reached the end of the file and have not found any
** matches. Do an "insert" for everything that does not match */
putInt(lenOut-base, &zDelta);
*(zDelta++) = ':';
memcpy(zDelta, &zOut[base], lenOut-base);
zDelta += lenOut-base;
base = lenOut;
break;
}
/* Advance the hash by one character. Keep looking for a match */
hash_next(&h, zOut[base+i+NHASH]);
i++;
}
}
/* Output a final "insert" record to get all the text at the end of
** the file that does not match anything in the source file.
*/
if( base<lenOut ){
putInt(lenOut-base, &zDelta);
*(zDelta++) = ':';
memcpy(zDelta, &zOut[base], lenOut-base);
zDelta += lenOut-base;
}
/* Output the final checksum record. */
putInt(checksum(zOut, lenOut), &zDelta);
*(zDelta++) = ';';
sqlite3_free(collide);
return zDelta - zOrigDelta;
}
/*
** Return the size (in bytes) of the output from applying
** a delta.
**
** This routine is provided so that an procedure that is able
** to call delta_apply() can learn how much space is required
** for the output and hence allocate nor more space that is really
** needed.
*/
static int delta_output_size(const char *zDelta, int lenDelta){
int size;
size = deltaGetInt(&zDelta, &lenDelta);
if( *zDelta!='\n' ){
/* ERROR: size integer not terminated by "\n" */
return -1;
}
return size;
}
/*
** Apply a delta.
**
** The output buffer should be big enough to hold the whole output
** file and a NUL terminator at the end. The delta_output_size()
** routine will determine this size for you.
**
** The delta string should be null-terminated. But the delta string
** may contain embedded NUL characters (if the input and output are
** binary files) so we also have to pass in the length of the delta in
** the lenDelta parameter.
**
** This function returns the size of the output file in bytes (excluding
** the final NUL terminator character). Except, if the delta string is
** malformed or intended for use with a source file other than zSrc,
** then this routine returns -1.
**
** Refer to the delta_create() documentation above for a description
** of the delta file format.
*/
static int delta_apply(
const char *zSrc, /* The source or pattern file */
int lenSrc, /* Length of the source file */
const char *zDelta, /* Delta to apply to the pattern */
int lenDelta, /* Length of the delta */
char *zOut /* Write the output into this preallocated buffer */
){
unsigned int limit;
unsigned int total = 0;
#ifdef FOSSIL_ENABLE_DELTA_CKSUM_TEST
char *zOrigOut = zOut;
#endif
limit = deltaGetInt(&zDelta, &lenDelta);
if( *zDelta!='\n' ){
/* ERROR: size integer not terminated by "\n" */
return -1;
}
zDelta++; lenDelta--;
while( *zDelta && lenDelta>0 ){
unsigned int cnt, ofst;
cnt = deltaGetInt(&zDelta, &lenDelta);
switch( zDelta[0] ){
case '@': {
zDelta++; lenDelta--;
ofst = deltaGetInt(&zDelta, &lenDelta);
if( lenDelta>0 && zDelta[0]!=',' ){
/* ERROR: copy command not terminated by ',' */
return -1;
}
zDelta++; lenDelta--;
total += cnt;
if( total>limit ){
/* ERROR: copy exceeds output file size */
return -1;
}
if( ofst+cnt > lenSrc ){
/* ERROR: copy extends past end of input */
return -1;
}
memcpy(zOut, &zSrc[ofst], cnt);
zOut += cnt;
break;
}
case ':': {
zDelta++; lenDelta--;
total += cnt;
if( total>limit ){
/* ERROR: insert command gives an output larger than predicted */
return -1;
}
if( cnt>lenDelta ){
/* ERROR: insert count exceeds size of delta */
return -1;
}
memcpy(zOut, zDelta, cnt);
zOut += cnt;
zDelta += cnt;
lenDelta -= cnt;
break;
}
case ';': {
zDelta++; lenDelta--;
zOut[0] = 0;
#ifdef FOSSIL_ENABLE_DELTA_CKSUM_TEST
if( cnt!=checksum(zOrigOut, total) ){
/* ERROR: bad checksum */
return -1;
}
#endif
if( total!=limit ){
/* ERROR: generated size does not match predicted size */
return -1;
}
return total;
}
default: {
/* ERROR: unknown delta operator */
return -1;
}
}
}
/* ERROR: unterminated delta */
return -1;
}
/*
** SQL functions: delta_create(X,Y)
**
** Return a delta for carrying X into Y.
*/
static void deltaCreateFunc(
sqlite3_context *context,
int argc,
sqlite3_value **argv
){
const char *aOrig; int nOrig; /* old blob */
const char *aNew; int nNew; /* new blob */
char *aOut; int nOut; /* output delta */
assert( argc==2 );
if( sqlite3_value_type(argv[0])==SQLITE_NULL ) return;
if( sqlite3_value_type(argv[1])==SQLITE_NULL ) return;
nOrig = sqlite3_value_bytes(argv[0]);
aOrig = (const char*)sqlite3_value_blob(argv[0]);
nNew = sqlite3_value_bytes(argv[1]);
aNew = (const char*)sqlite3_value_blob(argv[1]);
aOut = sqlite3_malloc64(nNew+70);
if( aOut==0 ){
sqlite3_result_error_nomem(context);
}else{
nOut = delta_create(aOrig, nOrig, aNew, nNew, aOut);
if( nOut<0 ){
sqlite3_free(aOut);
sqlite3_result_error(context, "cannot create fossil delta", -1);
}else{
sqlite3_result_blob(context, aOut, nOut, sqlite3_free);
}
}
}
/*
** SQL functions: delta_apply(X,D)
**
** Return the result of applying delta D to input X.
*/
static void deltaApplyFunc(
sqlite3_context *context,
int argc,
sqlite3_value **argv
){
const char *aOrig; int nOrig; /* The X input */
const char *aDelta; int nDelta; /* The input delta (D) */
char *aOut; int nOut, nOut2; /* The output */
assert( argc==2 );
if( sqlite3_value_type(argv[0])==SQLITE_NULL ) return;
if( sqlite3_value_type(argv[1])==SQLITE_NULL ) return;
nOrig = sqlite3_value_bytes(argv[0]);
aOrig = (const char*)sqlite3_value_blob(argv[0]);
nDelta = sqlite3_value_bytes(argv[1]);
aDelta = (const char*)sqlite3_value_blob(argv[1]);
/* Figure out the size of the output */
nOut = delta_output_size(aDelta, nDelta);
if( nOut<0 ){
sqlite3_result_error(context, "corrupt fossil delta", -1);
return;
}
aOut = sqlite3_malloc64((sqlite3_int64)nOut+1);
if( aOut==0 ){
sqlite3_result_error_nomem(context);
}else{
nOut2 = delta_apply(aOrig, nOrig, aDelta, nDelta, aOut);
if( nOut2!=nOut ){
sqlite3_free(aOut);
sqlite3_result_error(context, "corrupt fossil delta", -1);
}else{
sqlite3_result_blob(context, aOut, nOut, sqlite3_free);
}
}
}
/*
** SQL functions: delta_output_size(D)
**
** Return the size of the output that results from applying delta D.
*/
static void deltaOutputSizeFunc(
sqlite3_context *context,
int argc,
sqlite3_value **argv
){
const char *aDelta; int nDelta; /* The input delta (D) */
int nOut; /* Size of output */
assert( argc==1 );
if( sqlite3_value_type(argv[0])==SQLITE_NULL ) return;
nDelta = sqlite3_value_bytes(argv[0]);
aDelta = (const char*)sqlite3_value_blob(argv[0]);
/* Figure out the size of the output */
nOut = delta_output_size(aDelta, nDelta);
if( nOut<0 ){
sqlite3_result_error(context, "corrupt fossil delta", -1);
return;
}else{
sqlite3_result_int(context, nOut);
}
}
/*****************************************************************************
** Table-valued SQL function: delta_parse(DELTA)
**
** Schema:
**
** CREATE TABLE delta_parse(
** op TEXT,
** a1 INT,
** a2 ANY,
** delta HIDDEN BLOB
** );
**
** Given an input DELTA, this function parses the delta and returns
** rows for each entry in the delta. The op column has one of the
** values SIZE, COPY, INSERT, CHECKSUM, ERROR.
**
** Assuming no errors, the first row has op='SIZE'. a1 is the size of
** the output in bytes and a2 is NULL.
**
** After the initial SIZE row, there are zero or more 'COPY' and/or 'INSERT'
** rows. A COPY row means content is copied from the source into the
** output. Column a1 is the number of bytes to copy and a2 is the offset
** into source from which to begin copying. An INSERT row means to
** insert text into the output stream. Column a1 is the number of bytes
** to insert and column is a BLOB that contains the text to be inserted.
**
** The last row of a well-formed delta will have an op value of 'CHECKSUM'.
** The a1 column will be the value of the checksum and a2 will be NULL.
**
** If the input delta is not well-formed, then a row with an op value
** of 'ERROR' is returned. The a1 value of the ERROR row is the offset
** into the delta where the error was encountered and a2 is NULL.
*/
typedef struct deltaparsevtab_vtab deltaparsevtab_vtab;
typedef struct deltaparsevtab_cursor deltaparsevtab_cursor;
struct deltaparsevtab_vtab {
sqlite3_vtab base; /* Base class - must be first */
/* No additional information needed */
};
struct deltaparsevtab_cursor {
sqlite3_vtab_cursor base; /* Base class - must be first */
char *aDelta; /* The delta being parsed */
int nDelta; /* Number of bytes in the delta */
int iCursor; /* Current cursor location */
int eOp; /* Name of current operator */
unsigned int a1, a2; /* Arguments to current operator */
int iNext; /* Next cursor value */
};
/* Operator names:
*/
static const char *azOp[] = {
"SIZE", "COPY", "INSERT", "CHECKSUM", "ERROR", "EOF"
};
#define DELTAPARSE_OP_SIZE 0
#define DELTAPARSE_OP_COPY 1
#define DELTAPARSE_OP_INSERT 2
#define DELTAPARSE_OP_CHECKSUM 3
#define DELTAPARSE_OP_ERROR 4
#define DELTAPARSE_OP_EOF 5
/*
** The deltaparsevtabConnect() method is invoked to create a new
** deltaparse virtual table.
**
** Think of this routine as the constructor for deltaparsevtab_vtab objects.
**
** All this routine needs to do is:
**
** (1) Allocate the deltaparsevtab_vtab object and initialize all fields.
**
** (2) Tell SQLite (via the sqlite3_declare_vtab() interface) what the
** result set of queries against the virtual table will look like.
*/
static int deltaparsevtabConnect(
sqlite3 *db,
void *pAux,
int argc, const char *const*argv,
sqlite3_vtab **ppVtab,
char **pzErr
){
deltaparsevtab_vtab *pNew;
int rc;
rc = sqlite3_declare_vtab(db,
"CREATE TABLE x(op,a1,a2,delta HIDDEN)"
);
/* For convenience, define symbolic names for the index to each column. */
#define DELTAPARSEVTAB_OP 0
#define DELTAPARSEVTAB_A1 1
#define DELTAPARSEVTAB_A2 2
#define DELTAPARSEVTAB_DELTA 3
if( rc==SQLITE_OK ){
pNew = sqlite3_malloc64( sizeof(*pNew) );
*ppVtab = (sqlite3_vtab*)pNew;
if( pNew==0 ) return SQLITE_NOMEM;
memset(pNew, 0, sizeof(*pNew));
sqlite3_vtab_config(db, SQLITE_VTAB_INNOCUOUS);
}
return rc;
}
/*
** This method is the destructor for deltaparsevtab_vtab objects.
*/
static int deltaparsevtabDisconnect(sqlite3_vtab *pVtab){
deltaparsevtab_vtab *p = (deltaparsevtab_vtab*)pVtab;
sqlite3_free(p);
return SQLITE_OK;
}
/*
** Constructor for a new deltaparsevtab_cursor object.
*/
static int deltaparsevtabOpen(sqlite3_vtab *p, sqlite3_vtab_cursor **ppCursor){
deltaparsevtab_cursor *pCur;
pCur = sqlite3_malloc( sizeof(*pCur) );
if( pCur==0 ) return SQLITE_NOMEM;
memset(pCur, 0, sizeof(*pCur));
*ppCursor = &pCur->base;
return SQLITE_OK;
}
/*
** Destructor for a deltaparsevtab_cursor.
*/
static int deltaparsevtabClose(sqlite3_vtab_cursor *cur){
deltaparsevtab_cursor *pCur = (deltaparsevtab_cursor*)cur;
sqlite3_free(pCur->aDelta);
sqlite3_free(pCur);
return SQLITE_OK;
}
/*
** Advance a deltaparsevtab_cursor to its next row of output.
*/
static int deltaparsevtabNext(sqlite3_vtab_cursor *cur){
deltaparsevtab_cursor *pCur = (deltaparsevtab_cursor*)cur;
const char *z;
int i = 0;
pCur->iCursor = pCur->iNext;
z = pCur->aDelta + pCur->iCursor;
pCur->a1 = deltaGetInt(&z, &i);
switch( z[0] ){
case '@': {
z++;
pCur->a2 = deltaGetInt(&z, &i);
pCur->eOp = DELTAPARSE_OP_COPY;
pCur->iNext = (int)(&z[1] - pCur->aDelta);
break;
}
case ':': {
z++;
pCur->a2 = (unsigned int)(z - pCur->aDelta);
pCur->eOp = DELTAPARSE_OP_INSERT;
pCur->iNext = (int)(&z[pCur->a1] - pCur->aDelta);
break;
}
case ';': {
pCur->eOp = DELTAPARSE_OP_CHECKSUM;
pCur->iNext = pCur->nDelta;
break;
}
default: {
if( pCur->iNext==pCur->nDelta ){
pCur->eOp = DELTAPARSE_OP_EOF;
}else{
pCur->eOp = DELTAPARSE_OP_ERROR;
pCur->iNext = pCur->nDelta;
}
break;
}
}
return SQLITE_OK;
}
/*
** Return values of columns for the row at which the deltaparsevtab_cursor
** is currently pointing.
*/
static int deltaparsevtabColumn(
sqlite3_vtab_cursor *cur, /* The cursor */
sqlite3_context *ctx, /* First argument to sqlite3_result_...() */
int i /* Which column to return */
){
deltaparsevtab_cursor *pCur = (deltaparsevtab_cursor*)cur;
switch( i ){
case DELTAPARSEVTAB_OP: {
sqlite3_result_text(ctx, azOp[pCur->eOp], -1, SQLITE_STATIC);
break;
}
case DELTAPARSEVTAB_A1: {
sqlite3_result_int(ctx, pCur->a1);
break;
}
case DELTAPARSEVTAB_A2: {
if( pCur->eOp==DELTAPARSE_OP_COPY ){
sqlite3_result_int(ctx, pCur->a2);
}else if( pCur->eOp==DELTAPARSE_OP_INSERT ){
sqlite3_result_blob(ctx, pCur->aDelta+pCur->a2, pCur->a1,
SQLITE_TRANSIENT);
}
break;
}
case DELTAPARSEVTAB_DELTA: {
sqlite3_result_blob(ctx, pCur->aDelta, pCur->nDelta, SQLITE_TRANSIENT);
break;
}
}
return SQLITE_OK;
}
/*
** Return the rowid for the current row. In this implementation, the
** rowid is the same as the output value.
*/
static int deltaparsevtabRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
deltaparsevtab_cursor *pCur = (deltaparsevtab_cursor*)cur;
*pRowid = pCur->iCursor;
return SQLITE_OK;
}
/*
** Return TRUE if the cursor has been moved off of the last
** row of output.
*/
static int deltaparsevtabEof(sqlite3_vtab_cursor *cur){
deltaparsevtab_cursor *pCur = (deltaparsevtab_cursor*)cur;
return pCur->eOp==DELTAPARSE_OP_EOF;
}
/*
** This method is called to "rewind" the deltaparsevtab_cursor object back
** to the first row of output. This method is always called at least
** once prior to any call to deltaparsevtabColumn() or deltaparsevtabRowid() or
** deltaparsevtabEof().
*/
static int deltaparsevtabFilter(
sqlite3_vtab_cursor *pVtabCursor,
int idxNum, const char *idxStr,
int argc, sqlite3_value **argv
){
deltaparsevtab_cursor *pCur = (deltaparsevtab_cursor *)pVtabCursor;
const char *a;
int i = 0;
pCur->eOp = DELTAPARSE_OP_ERROR;
if( idxNum!=1 ){
return SQLITE_OK;
}
pCur->nDelta = sqlite3_value_bytes(argv[0]);
a = (const char*)sqlite3_value_blob(argv[0]);
if( pCur->nDelta==0 || a==0 ){
return SQLITE_OK;
}
pCur->aDelta = sqlite3_malloc64( pCur->nDelta+1 );
if( pCur->aDelta==0 ){
pCur->nDelta = 0;
return SQLITE_NOMEM;
}
memcpy(pCur->aDelta, a, pCur->nDelta);
pCur->aDelta[pCur->nDelta] = 0;
a = pCur->aDelta;
pCur->eOp = DELTAPARSE_OP_SIZE;
pCur->a1 = deltaGetInt(&a, &i);
if( a[0]!='\n' ){
pCur->eOp = DELTAPARSE_OP_ERROR;
pCur->a1 = pCur->a2 = 0;
pCur->iNext = pCur->nDelta;
return SQLITE_OK;
}
a++;
pCur->iNext = (unsigned int)(a - pCur->aDelta);
return SQLITE_OK;
}
/*
** SQLite will invoke this method one or more times while planning a query
** that uses the virtual table. This routine needs to create
** a query plan for each invocation and compute an estimated cost for that
** plan.
*/
static int deltaparsevtabBestIndex(
sqlite3_vtab *tab,
sqlite3_index_info *pIdxInfo
){
int i;
for(i=0; i<pIdxInfo->nConstraint; i++){
if( pIdxInfo->aConstraint[i].iColumn != DELTAPARSEVTAB_DELTA ) continue;
if( pIdxInfo->aConstraint[i].usable==0 ) continue;
if( pIdxInfo->aConstraint[i].op!=SQLITE_INDEX_CONSTRAINT_EQ ) continue;
pIdxInfo->aConstraintUsage[i].argvIndex = 1;
pIdxInfo->aConstraintUsage[i].omit = 1;
pIdxInfo->estimatedCost = (double)1;
pIdxInfo->estimatedRows = 10;
pIdxInfo->idxNum = 1;
return SQLITE_OK;
}
pIdxInfo->idxNum = 0;
pIdxInfo->estimatedCost = (double)0x7fffffff;
pIdxInfo->estimatedRows = 0x7fffffff;
return SQLITE_CONSTRAINT;
}
/*
** This following structure defines all the methods for the
** virtual table.
*/
static sqlite3_module deltaparsevtabModule = {
/* iVersion */ 0,
/* xCreate */ 0,
/* xConnect */ deltaparsevtabConnect,
/* xBestIndex */ deltaparsevtabBestIndex,
/* xDisconnect */ deltaparsevtabDisconnect,
/* xDestroy */ 0,
/* xOpen */ deltaparsevtabOpen,
/* xClose */ deltaparsevtabClose,
/* xFilter */ deltaparsevtabFilter,
/* xNext */ deltaparsevtabNext,
/* xEof */ deltaparsevtabEof,
/* xColumn */ deltaparsevtabColumn,
/* xRowid */ deltaparsevtabRowid,
/* xUpdate */ 0,
/* xBegin */ 0,
/* xSync */ 0,
/* xCommit */ 0,
/* xRollback */ 0,
/* xFindMethod */ 0,
/* xRename */ 0,
/* xSavepoint */ 0,
/* xRelease */ 0,
/* xRollbackTo */ 0,
/* xShadowName */ 0,
/* xIntegrity */ 0
};
#ifdef _WIN32
__declspec(dllexport)
#endif
int sqlite3_fossildelta_init(
sqlite3 *db,
char **pzErrMsg,
const sqlite3_api_routines *pApi
){
static const int enc = SQLITE_UTF8|SQLITE_INNOCUOUS;
int rc = SQLITE_OK;
SQLITE_EXTENSION_INIT2(pApi);
(void)pzErrMsg; /* Unused parameter */
rc = sqlite3_create_function(db, "delta_create", 2, enc, 0,
deltaCreateFunc, 0, 0);
if( rc==SQLITE_OK ){
rc = sqlite3_create_function(db, "delta_apply", 2, enc, 0,
deltaApplyFunc, 0, 0);
}
if( rc==SQLITE_OK ){
rc = sqlite3_create_function(db, "delta_output_size", 1, enc, 0,
deltaOutputSizeFunc, 0, 0);
}
if( rc==SQLITE_OK ){
rc = sqlite3_create_module(db, "delta_parse", &deltaparsevtabModule, 0);
}
return rc;
}
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