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/*
** 2019-03-30
**
** 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.
**
******************************************************************************
**
** An SQL function that uses the incremental BLOB I/O mechanism of SQLite
** to read or write part of a blob. This is intended for debugging use
** in the CLI.
**
** readblob(SCHEMA,TABLE,COLUMN,ROWID,OFFSET,N)
**
** Returns N bytes of the blob starting at OFFSET.
**
** writeblob(SCHEMA,TABLE,COLUMN,ROWID,OFFSET,NEWDATA)
**
** NEWDATA must be a blob. The content of NEWDATA overwrites the
** existing BLOB data at SCHEMA.TABLE.COLUMN for row ROWID beginning
** at OFFSET bytes into the blob.
*/
#include "sqlite3ext.h"
SQLITE_EXTENSION_INIT1
#include <assert.h>
#include <string.h>
static void readblobFunc(
sqlite3_context *context,
int argc,
sqlite3_value **argv
){
sqlite3_blob *pBlob = 0;
const char *zSchema;
const char *zTable;
const char *zColumn;
sqlite3_int64 iRowid;
int iOfst;
unsigned char *aData;
int nData;
sqlite3 *db;
int rc;
zSchema = (const char*)sqlite3_value_text(argv[0]);
zTable = (const char*)sqlite3_value_text(argv[1]);
if( zTable==0 ){
sqlite3_result_error(context, "bad table name", -1);
return;
}
zColumn = (const char*)sqlite3_value_text(argv[2]);
if( zTable==0 ){
sqlite3_result_error(context, "bad column name", -1);
return;
}
iRowid = sqlite3_value_int64(argv[3]);
iOfst = sqlite3_value_int(argv[4]);
nData = sqlite3_value_int(argv[5]);
if( nData<=0 ) return;
aData = sqlite3_malloc64( nData+1 );
if( aData==0 ){
sqlite3_result_error_nomem(context);
return;
}
db = sqlite3_context_db_handle(context);
rc = sqlite3_blob_open(db, zSchema, zTable, zColumn, iRowid, 0, &pBlob);
if( rc ){
sqlite3_free(aData);
sqlite3_result_error(context, "cannot open BLOB pointer", -1);
return;
}
rc = sqlite3_blob_read(pBlob, aData, nData, iOfst);
sqlite3_blob_close(pBlob);
if( rc ){
sqlite3_free(aData);
sqlite3_result_error(context, "BLOB read failed", -1);
}else{
sqlite3_result_blob(context, aData, nData, sqlite3_free);
}
}
static void writeblobFunc(
sqlite3_context *context,
int argc,
sqlite3_value **argv
){
sqlite3_blob *pBlob = 0;
const char *zSchema;
const char *zTable;
const char *zColumn;
sqlite3_int64 iRowid;
int iOfst;
unsigned char *aData;
int nData;
sqlite3 *db;
int rc;
zSchema = (const char*)sqlite3_value_text(argv[0]);
zTable = (const char*)sqlite3_value_text(argv[1]);
if( zTable==0 ){
sqlite3_result_error(context, "bad table name", -1);
return;
}
zColumn = (const char*)sqlite3_value_text(argv[2]);
if( zTable==0 ){
sqlite3_result_error(context, "bad column name", -1);
return;
}
iRowid = sqlite3_value_int64(argv[3]);
iOfst = sqlite3_value_int(argv[4]);
if( sqlite3_value_type(argv[5])!=SQLITE_BLOB ){
sqlite3_result_error(context, "6th argument must be a BLOB", -1);
return;
}
nData = sqlite3_value_bytes(argv[5]);
aData = (unsigned char *)sqlite3_value_blob(argv[5]);
db = sqlite3_context_db_handle(context);
rc = sqlite3_blob_open(db, zSchema, zTable, zColumn, iRowid, 1, &pBlob);
if( rc ){
sqlite3_result_error(context, "cannot open BLOB pointer", -1);
return;
}
rc = sqlite3_blob_write(pBlob, aData, nData, iOfst);
sqlite3_blob_close(pBlob);
if( rc ){
sqlite3_result_error(context, "BLOB write failed", -1);
}
}
#ifdef _WIN32
__declspec(dllexport)
#endif
int sqlite3_blobio_init(
sqlite3 *db,
char **pzErrMsg,
const sqlite3_api_routines *pApi
){
int rc = SQLITE_OK;
SQLITE_EXTENSION_INIT2(pApi);
(void)pzErrMsg; /* Unused parameter */
rc = sqlite3_create_function(db, "readblob", 6, SQLITE_UTF8, 0,
readblobFunc, 0, 0);
if( rc==SQLITE_OK ){
rc = sqlite3_create_function(db, "writeblob", 6, SQLITE_UTF8, 0,
writeblobFunc, 0, 0);
}
return rc;
}
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