The write operation using the open sqlite3_blob object fails after some
other field in the same row is updated.
The testcase below illustrates the problem.
Yuri
---testcase---
#include <stdio.h>
#include <stdlib.h>
#include "sqlite3.h"
int main(int argc, char **argv) {
if(argc < 2) {
fprintf(stderr, "Usage: %s <dbname> <filename>\n",
argv[0]);
exit(1);
}
// file to insert
FILE *f = fopen(argv[2], "rb");
if(NULL == f) {
fprintf(stderr, "Couldn't open file %s\n", argv[2]);
exit(1);
}
// Calculate size of file
fseek(f, 0, SEEK_END);
long filesize = ftell(f);
fseek(f, 0, SEEK_SET);
// Table name we're going to use
char tablename[] = "testblob";
char columnname[] = "blobby";
// Actual database handle
sqlite3 *db = NULL;
// Database commands
char create_sql[1024];
snprintf(create_sql, sizeof(create_sql), "CREATE TABLE IF NOT
EXISTS %s ("
"id INTEGER PRIMARY KEY, fld INTEGER, %s
BLOB)", tablename, columnname);
// Going to insert a zeroblob of the size of the file
char insert_sql[1024];
snprintf(insert_sql, sizeof(insert_sql), "INSERT INTO %s (%s)
VALUES (?)", tablename, columnname);
// SQLite return value
int rc;
// Open the database
rc = sqlite3_open(argv[1], &db);
if(SQLITE_OK != rc) {
fprintf(stderr, "Can't open database %s (%i): %s\n",
argv[1], rc, sqlite3_errmsg(db));
exit(1);
}
char *exec_errmsg;
rc = sqlite3_exec(db, create_sql, NULL, NULL, &exec_errmsg);
if(SQLITE_OK != rc) {
fprintf(stderr, "Can't create table (%i): %s\n", rc,
sqlite3_errmsg(db));
sqlite3_close(db);
exit(1);
}
sqlite3_stmt *insert_stmt;
rc = sqlite3_prepare_v2(db, insert_sql, -1, &insert_stmt, NULL);
if(SQLITE_OK != rc) {
fprintf(stderr, "Can't prepare insert statment %s (%i):
%s\n", insert_sql, rc, sqlite3_errmsg(db));
sqlite3_close(db);
exit(1);
}
// Bind a block of zeros the size of the file we're going to
insert later
sqlite3_bind_zeroblob(insert_stmt, 1, filesize);
if(SQLITE_DONE != (rc = sqlite3_step(insert_stmt))) {
fprintf(stderr, "Insert statement didn't work (%i):
%s\n", rc, sqlite3_errmsg(db));
exit(1);
}
sqlite3_int64 rowid = sqlite3_last_insert_rowid(db);
printf("Created a row, id %i, with a blank blob size %i\n",
(int)rowid, (int)filesize);
sqlite3_blob *blob;
rc = sqlite3_blob_open(db, "main", tablename, columnname,
rowid, 1, &blob);
if(SQLITE_OK != rc) {
fprintf(stderr, "Couldn't get blob handle (%i): %s\n",
rc, sqlite3_errmsg(db));
exit(1);
}
const int BLOCKSIZE = 1024;
int len;
void *block = malloc(BLOCKSIZE);
int offset = 0;
while(0 < (len = fread(block, 1, BLOCKSIZE, f))) {
if(SQLITE_OK != (rc = sqlite3_blob_write(blob, block,
len, offset))) {
fprintf(stderr, "Error writing to blob handle.
Offset %i, len %i, rc=%d\n", offset, len, rc);
exit(1);
}
offset+=len;
printf("... wrote block @off=%d\n", offset);
// update that breaks the following sqlite3_blob_write
if(SQLITE_OK != (rc = sqlite3_exec(db, "UPDATE testblob
SET fld=1", NULL, NULL, &exec_errmsg))) {
fprintf(stderr, "Error while updating the
integer field, error=%d\n", rc);
exit(1);
}
}
sqlite3_blob_close(blob);
printf("Successfully wrote to blob\n");
free(block);
fclose(f);
sqlite3_finalize(insert_stmt);
sqlite3_close(db);
return 0;
}
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