In my iOS app I read a large CSV file and load it (via inserts) in a SQLite database.
This is my code:
- (void) parseCSVFile:(NSString *)path
{
__block BOOL isFileOk = NO;
__block BOOL atLeastOneRowProcessed = NO;
NSFileManager *fileMgr = [[NSFileManager alloc] init];
unsigned long totalSize = [[[fileMgr attributesOfItemAtPath:path error:nil] objectForKey:@"NSFileSize"] intValue];
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *writableDBPath = [documentsDirectory stringByAppendingPathComponent:@"mydatabase.sqlite"];
const char *dbpath = [writableDBPath UTF8String];
dispatch_queue_t databaseQueue = [(AppDelegate *)[[UIApplication sharedApplication] delegate] databaseQueue];
dispatch_sync(databaseQueue, ^{
sqlite3 *ddbb;
NSLog(@"INIT DATABASE");
if (sqlite3_open(dbpath, &ddbb) == SQLITE_OK)
{
char* errorMessage;
sqlite3_exec(ddbb, "DROP TABLE IF EXISTS datainfile", NULL, NULL, &errorMessage);
sqlite3_exec(ddbb, "CREATE TABLE \"datainfile\" (\"field1\" TEXT PRIMARY KEY NOT NULL ,\"field2\" TEXT DEFAULT (null) ,\"field3\" TEXT DEFAULT (null) ,\"field4\" TEXT)", NULL, NULL, &errorMessage);
sqlite3_exec(ddbb, "BEGIN TRANSACTION", NULL, NULL, &errorMessage);
char buffer[] = "INSERT OR IGNORE INTO datainfile VALUES (?1, ?2, ?3, ?4)";
sqlite3_stmt* stmt;
sqlite3_prepare_v2(ddbb, buffer, (int)strlen(buffer), &stmt, NULL);
char *pathUTF8 = (char*)[path UTF8String];
FILE* stream = fopen(pathUTF8, "r");
char *field1 = "";
char *field2 = "";
char *field3 = "";
char *field4 = "";
NSLog(@"READING FILE");
unsigned long processedSize = 0;
char line[1024];
while(fgets(line, 1024, stream))
{
processedSize = processedSize + strlen(line) * sizeof(char);
char* tmp = strdup(line);
field1 = strtok (tmp,", \t");
field2 = strtok (NULL, ", \t");
field3 = strtok (NULL, ", \t");
field4 = strtok (NULL, "\r\n");
atLeastOneRowProcessed = YES;
if(!isFileOk)
{
isFileOk = [self checkIfFileIsACorrectCSVWithField1:field1 field2:field2 field3:field3 andField4:field4];
if(!isFileOk)
{
if([_delegate respondsToSelector:@selector(fileParserError:)])
[_delegate fileParserError:_reportErrorMessage];
free(tmp);
break;
}
}
sqlite3_bind_text(stmt, 1, field1, -1, SQLITE_STATIC);
sqlite3_bind_text(stmt, 2, field2, -1, SQLITE_STATIC);
sqlite3_bind_text(stmt, 3, field3, -1, SQLITE_STATIC);
sqlite3_bind_text(stmt, 4, field4, -1, SQLITE_STATIC);
if (sqlite3_step(stmt) != SQLITE_DONE)
{
NSLog(@"ERROR: Commit Failed in line %s!\n", line);
// If there was an error we try to repeat the commit
sqlite3_reset(stmt);
sqlite3_bind_text(stmt, 1, field1, -1, SQLITE_STATIC);
sqlite3_bind_text(stmt, 2, field2, -1, SQLITE_STATIC);
sqlite3_bind_text(stmt, 3, field3, -1, SQLITE_STATIC);
sqlite3_bind_text(stmt, 4, field4, -1, SQLITE_STATIC);
if (sqlite3_step(stmt) != SQLITE_DONE)
{
NSLog(@"ERROR: Commit failed again");
}
else
{
NSLog(@"ERROR: Commit success");
}
}
sqlite3_reset(stmt);
free(tmp);
}
if(isFileOk)
{
NSLog(@"File read and now the commit starts");
sqlite3_exec(ddbb, "COMMIT TRANSACTION", NULL, NULL, &errorMessage);
_phase = PARSER_PHASE_CREATING_INDEX;
sqlite3_exec(ddbb, "CREATE INDEX field1 ON datainfile(field1);", NULL, NULL, &errorMessage);
sqlite3_finalize(stmt);
NSLog(@"Commit has ended");
}
}
sqlite3_close(ddbb);
});
if(isFileOk)
{
if([_delegate respondsToSelector:@selector(fileParserFinished)])
[_delegate fileParserFinished];
}
else
{
if(!atLeastOneRowProcessed)
{
_reportErrorMessage = NSLocalizedString(@"TXT_FILEERROR_NOPROCESSED", Nil);
if([_delegate respondsToSelector:@selector(fileParserError:)])
[_delegate fileParserError:_reportErrorMessage];
}
}
}
databaseQueue is an attribute of AppDelegate created this way:
_databaseQueue = dispatch_queue_create("com.mycompany.myapp.database", 0);
Well, this is working well almost always. But sometimes it happens a strange crash. This is the log:
Crashed: com.mycompany.myapp.database
0 libsystem_kernel.dylib 0x1865d1014 __pthread_kill + 8
1 libsystem_pthread.dylib 0x18669b264 pthread_kill + 112
2 libsystem_c.dylib 0x1865459c4 abort + 140
3 libsystem_c.dylib 0x186545ad8 _UTF2_init + 82
4 libsystem_c.dylib 0x186559c7c __chk_fail_overlap + 54
5 libsystem_c.dylib 0x186559c44 __chk_fail + 18
6 libsystem_c.dylib 0x18655a04c __vsprintf_chk + 134
7 MyApp 0x1000c151c __32-[FileParser parseCSVFile:]_block_invoke (FileParser.m:650)
8 libdispatch.dylib 0x18648e9a0 _dispatch_client_callout + 16
9 libdispatch.dylib 0x18649bee0 _dispatch_barrier_sync_f_invoke + 84
10 MyApp 0x1000c1084 -[FileParser parseCSVFile:] (FileParser.m:734)
11 MyApp 0x1000bed28 -[FileParser readFileWithPath:andDelegate:] (FileParser.m:147)
12 MyApp 0x100041a64 __57-[HomeViewController readFileWithPath:]_block_invoke_2 (HomeViewController.m:625)
13 libdispatch.dylib 0x18648e9e0 _dispatch_call_block_and_release + 24
14 libdispatch.dylib 0x18648e9a0 _dispatch_client_callout + 16
15 libdispatch.dylib 0x18649d0d4 _dispatch_queue_override_invoke + 644
16 libdispatch.dylib 0x18649ea50 _dispatch_root_queue_drain + 540
17 libdispatch.dylib 0x18649e7d0 _dispatch_worker_thread3 + 124
18 libsystem_pthread.dylib 0x186697100 _pthread_wqthread + 1096
19 libsystem_pthread.dylib 0x186696cac start_wqthread + 4
It happens in the lines 734 and 650 of my FileParser, and these lines are:
(line 734) the second if(isFileOk)
Just the first line after leaving the dispatch_sync.
(line 650) processedSize = processedSize + strlen(line) * sizeof(char);
Reading the first line of the CSV file.
It seems to me like the dispatch_sync leaves its code before it's executed, calling "simultaneously" a line outside the block and one line inside the block.
I must add that when this crash has happened the line that crashed outside the block is always if(isFileOk), but the line that crashed inside the block varies.
What could it be happening?