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Diffstat (limited to '')
| -rw-r--r-- | ext/misc/blobio.c | 152 |
1 files changed, 152 insertions, 0 deletions
diff --git a/ext/misc/blobio.c b/ext/misc/blobio.c new file mode 100644 index 0000000..3a1ee84 --- /dev/null +++ b/ext/misc/blobio.c @@ -0,0 +1,152 @@ +/* +** 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; +} |