我试图将对64位整数的支持添加到我的Erlang SQLite 3包装器的分支中（因为这是SQLite 3使用的主要整数类型）。虽然看起来非常简单，但我遇到了一个问题。
这是带有调试语句的驱动程序C端的代码（有关其他文件，请参阅https://github.com/alexeyr/erlang-sqlite3/tree/64bit，但我认为此处包含问题）：
#include "sqlite3_drv.h"
// Callback Array
static ErlDrvEntry basic_driver_entry = {
NULL, /* init */
start, /* startup (defined below) */
stop, /* shutdown (defined below) */
NULL, /* output */
NULL, /* ready_input */
NULL, /* ready_output */
"sqlite3_drv", /* the name of the driver */
NULL, /* finish */
NULL, /* handle */
control, /* control */
NULL, /* timeout */
NULL, /* outputv (defined below) */
ready_async, /* ready_async */
NULL, /* flush */
NULL, /* call */
NULL, /* event */
ERL_DRV_EXTENDED_MARKER, /* ERL_DRV_EXTENDED_MARKER */
ERL_DRV_EXTENDED_MAJOR_VERSION, /* ERL_DRV_EXTENDED_MAJOR_VERSION */
ERL_DRV_EXTENDED_MAJOR_VERSION, /* ERL_DRV_EXTENDED_MINOR_VERSION */
ERL_DRV_FLAG_USE_PORT_LOCKING /* ERL_DRV_FLAGs */
};
DRIVER_INIT(basic_driver) {
return &basic_driver_entry;
}
// Driver Start
static ErlDrvData start(ErlDrvPort port, char* cmd) {
sqlite3_drv_t* retval = (sqlite3_drv_t*) driver_alloc(sizeof(sqlite3_drv_t));
struct sqlite3 *db = 0;
int status = 0;
retval->log = fopen ("/tmp/erlang-sqlite3-drv.log", "a+");
if (!retval->log) {
fprintf (stderr, "Can't create log file\n");
}
fprintf (retval->log, "--- Start erlang-sqlite3 driver\nCommand line: [%s]\n", cmd);
const char *db_name = strstr (cmd, " ");
if (!db_name) {
fprintf (retval->log, "ERROR: DB name should be passed at command line\n");
db_name = DB_PATH;
} else {
++db_name;
}
// Create and open the database
sqlite3_open(db_name, &db);
status = sqlite3_errcode(db);
if(status != SQLITE_OK) {
fprintf(retval->log, "ERROR: Unabled to open file: %s because %s\n\n", DB_PATH, sqlite3_errmsg(db));
} else {
fprintf(retval->log, "Opened file %s\n", db_name);
}
// Set the state for the driver
retval->port = port;
retval->db = db;
retval->key = 42; //FIXME: Just a magic number, make real key
#define STR_(ARG) #ARG
#define STR(ARG) STR_(ARG)
retval->atom_error = driver_mk_atom ("error");
retval->atom_columns = driver_mk_atom ("columns");
retval->atom_rows = driver_mk_atom ("rows");
retval->atom_null = driver_mk_atom (STR (NULL_ATOM));
retval->atom_id = driver_mk_atom ("id");
retval->atom_ok = driver_mk_atom ("ok");
retval->atom_unknown_cmd = driver_mk_atom ("uknown_command");
fflush (retval->log);
return (ErlDrvData) retval;
}
// Driver Stop
static void stop(ErlDrvData handle) {
sqlite3_drv_t* driver_data = (sqlite3_drv_t*) handle;
sqlite3_close(driver_data->db);
fclose (driver_data->log);
driver_data->log = 0;
driver_free(driver_data);
}
// Handle input from Erlang VM
static int control(ErlDrvData drv_data, unsigned int command, char *buf,
int len, char **rbuf, int rlen) {
sqlite3_drv_t* driver_data = (sqlite3_drv_t*) drv_data;
switch(command) {
case CMD_SQL_EXEC:
sql_exec(driver_data, buf, len);
break;
default:
unknown(driver_data, buf, len);
}
return 0;
}
static inline int return_error(sqlite3_drv_t *drv, const char *error, ErlDrvTermData **spec, int *terms_count) {
*spec = (ErlDrvTermData *)calloc(7, sizeof(ErlDrvTermData));
(*spec)[0] = ERL_DRV_ATOM;
(*spec)[1] = drv->atom_error;
(*spec)[2] = ERL_DRV_STRING;
(*spec)[3] = (ErlDrvTermData)error;
(*spec)[4] = strlen(error);
(*spec)[5] = ERL_DRV_TUPLE;
(*spec)[6] = 2;
*terms_count = 7;
return 0;
}
static int sql_exec(sqlite3_drv_t *drv, char *command, int command_size) {
int result, next_row;
char *rest = NULL;
sqlite3_stmt *statement;
// fprintf(drv->log, "Preexec: %.*s\n", command_size, command);
// fflush (drv->log);
result = sqlite3_prepare_v2(drv->db, command, command_size, &statement, (const char **)&rest);
if(result != SQLITE_OK) {
ErlDrvTermData *dataset;
int term_count;
return_error(drv, sqlite3_errmsg(drv->db), &dataset, &term_count);
driver_output_term(drv->port, dataset, term_count);
return 0;
}
async_sqlite3_command *async_command = (async_sqlite3_command *)calloc(1, sizeof(async_sqlite3_command));
async_command->driver_data = drv;
async_command->statement = statement;
// fprintf(drv->log, "Driver async: %d %p\n", SQLITE_VERSION_NUMBER, async_command->statement);
// fflush (drv->log);
if (sqlite3_threadsafe()) {
drv->async_handle = driver_async(drv->port, &drv->key, sql_exec_async, async_command, sql_free_async);
} else {
sql_exec_async(async_command);
ready_async((ErlDrvData)drv, (ErlDrvThreadData)async_command);
}
return 0;
}
static void sql_free_async(void *_async_command)
{
int i;
async_sqlite3_command *async_command = (async_sqlite3_command *)_async_command;
free(async_command->dataset);
async_command->driver_data->async_handle = 0;
if (async_command->int64s) {
free(async_command->int64s);
}
if (async_command->floats) {
free(async_command->floats);
}
for (i = 0; i < async_command->binaries_count; i++) {
driver_free_binary(async_command->binaries[i]);
}
if(async_command->binaries) {
free(async_command->binaries);
}
if (async_command->statement) {
sqlite3_finalize(async_command->statement);
}
free(async_command);
}
static void sql_exec_async(void *_async_command) {
async_sqlite3_command *async_command = (async_sqlite3_command *)_async_command;
ErlDrvTermData *dataset = async_command->dataset;
int term_count = async_command->term_count;
int row_count = async_command->row_count;
sqlite3_drv_t *drv = async_command->driver_data;
int result, next_row, column_count;
char *error = NULL;
char *rest = NULL;
sqlite3_stmt *statement = async_command->statement;
sqlite3_int64 *int64s = NULL;
int int64_count = 0;
double *floats = NULL;
int float_count = 0;
ErlDrvBinary **binaries = NULL;
int binaries_count = 0;
int i;
column_count = sqlite3_column_count(statement);
dataset = NULL;
term_count += 2;
dataset = realloc(dataset, sizeof(*dataset) * term_count);
dataset[term_count - 2] = ERL_DRV_PORT;
dataset[term_count - 1] = driver_mk_port(drv->port);
if (column_count > 0) {
int base = term_count;
term_count += 2 + column_count*3 + 1 + 2 + 2 + 2;
dataset = realloc(dataset, sizeof(*dataset) * term_count);
dataset[base] = ERL_DRV_ATOM;
dataset[base + 1] = drv->atom_columns;
for (i = 0; i < column_count; i++) {
char *column_name = (char *)sqlite3_column_name(statement, i);
// fprintf(drv->log, "Column: %s\n", column_name);
// fflush (drv->log);
dataset[base + 2 + (i*3)] = ERL_DRV_STRING;
dataset[base + 2 + (i*3) + 1] = (ErlDrvTermData) column_name;
dataset[base + 2 + (i*3) + 2] = strlen (column_name);
}
dataset[base + 2 + column_count*3 + 0] = ERL_DRV_NIL;
dataset[base + 2 + column_count*3 + 1] = ERL_DRV_LIST;
dataset[base + 2 + column_count*3 + 2] = column_count + 1;
dataset[base + 2 + column_count*3 + 3] = ERL_DRV_TUPLE;
dataset[base + 2 + column_count*3 + 4] = 2;
dataset[base + 2 + column_count*3 + 5] = ERL_DRV_ATOM;
dataset[base + 2 + column_count*3 + 6] = drv->atom_rows;
}
// fprintf(drv->log, "Exec: %s\n", sqlite3_sql(statement));
// fflush (drv->log);
while ((next_row = sqlite3_step(statement)) == SQLITE_ROW) {
for (i = 0; i < column_count; i++) {
// fprintf(drv->log, "Column %d type: %d\n", i, sqlite3_column_type(statement, i));
// fflush (drv->log);
switch (sqlite3_column_type(statement, i)) {
case SQLITE_INTEGER: {
int64_count++;
int64s = realloc(int64s, sizeof(sqlite3_int64) * int64_count);
int64s[int64_count - 1] = sqlite3_column_int64(statement, i);
term_count += 2;
dataset = realloc(dataset, sizeof(*dataset) * term_count);
dataset[term_count - 2] = ERL_DRV_INT64;
dataset[term_count - 1] = (ErlDrvTermData)&int64s[int64_count - 1];
printf("Dataset element: %lld\n", *((sqlite3_int64 *) dataset[term_count - 1]));
break;
}
case SQLITE_FLOAT: {
float_count++;
floats = realloc(floats, sizeof(double) * float_count);
floats[float_count - 1] = sqlite3_column_double(statement, i);
term_count += 2;
dataset = realloc(dataset, sizeof(*dataset) * term_count);
dataset[term_count - 2] = ERL_DRV_FLOAT;
dataset[term_count - 1] = (ErlDrvTermData)&floats[float_count - 1];
break;
}
case SQLITE_BLOB:
case SQLITE_TEXT: {
int bytes = sqlite3_column_bytes(statement, i);
binaries_count++;
binaries = realloc(binaries, sizeof(*binaries) * binaries_count);
binaries[binaries_count - 1] = driver_alloc_binary(bytes);
binaries[binaries_count - 1]->orig_size = bytes;
memcpy(binaries[binaries_count - 1]->orig_bytes, sqlite3_column_blob(statement, i), bytes);
term_count += 4;
dataset = realloc(dataset, sizeof(*dataset) * term_count);
dataset[term_count - 4] = ERL_DRV_BINARY;
dataset[term_count - 3] = (ErlDrvTermData)binaries[binaries_count - 1];
dataset[term_count - 2] = bytes;
dataset[term_count - 1] = 0;
break;
}
case SQLITE_NULL: {
term_count += 2;
dataset = realloc (dataset, sizeof (*dataset) * term_count);
dataset[term_count - 2] = ERL_DRV_ATOM;
dataset[term_count - 1] = drv->atom_null;
break;
}
}
}
term_count += 2;
dataset = realloc(dataset, sizeof(*dataset) * term_count);
dataset[term_count - 2] = ERL_DRV_TUPLE;
dataset[term_count - 1] = column_count;
row_count++;
}
async_command->row_count = row_count;
async_command->int64s = int64s;
async_command->floats = floats;
async_command->binaries = binaries;
async_command->binaries_count = binaries_count;
if (next_row == SQLITE_BUSY) {
return_error(drv, "SQLite3 database is busy", &async_command->dataset, &async_command->term_count);
return;
}
if (next_row != SQLITE_DONE) {
return_error(drv, sqlite3_errmsg(drv->db), &async_command->dataset, &async_command->term_count);
return;
}
if (column_count > 0) {
term_count += 3;
dataset = realloc(dataset, sizeof(*dataset) * term_count);
dataset[term_count - 3] = ERL_DRV_NIL;
dataset[term_count - 2] = ERL_DRV_LIST;
dataset[term_count - 1] = row_count + 1;
term_count += 2;
dataset = realloc(dataset, sizeof(*dataset) * term_count);
dataset[term_count - 2] = ERL_DRV_TUPLE;
dataset[term_count - 1] = 2;
term_count += 3;
dataset = realloc(dataset, sizeof(*dataset) * term_count);
dataset[term_count - 3] = ERL_DRV_NIL;
dataset[term_count - 2] = ERL_DRV_LIST;
dataset[term_count - 1] = 3;
} else if (strcasestr(sqlite3_sql(statement), "INSERT")) {
sqlite3_int64 rowid = sqlite3_last_insert_rowid(drv->db);
term_count += 6;
dataset = realloc(dataset, sizeof(*dataset) * term_count);
dataset[term_count - 6] = ERL_DRV_ATOM;
dataset[term_count - 5] = drv->atom_id;
dataset[term_count - 4] = ERL_DRV_INT;
dataset[term_count - 3] = rowid;
dataset[term_count - 2] = ERL_DRV_TUPLE;
dataset[term_count - 1] = 2;
} else {
term_count += 6;
dataset = realloc(dataset, sizeof(*dataset) * term_count);
dataset[term_count - 6] = ERL_DRV_ATOM;
dataset[term_count - 5] = drv->atom_ok;
dataset[term_count - 4] = ERL_DRV_INT;
dataset[term_count - 3] = next_row;
dataset[term_count - 2] = ERL_DRV_TUPLE;
dataset[term_count - 1] = 2;
}
term_count += 2;
dataset = realloc(dataset, sizeof(*dataset) * term_count);
dataset[term_count - 2] = ERL_DRV_TUPLE;
dataset[term_count - 1] = 2;
async_command->dataset = dataset;
async_command->term_count = term_count;
// fprintf(drv->log, "Total term count: %p %d, rows count: %dx%d\n", statement, term_count, column_count, row_count);
// fflush (drv->log);
}
static void ready_async(ErlDrvData drv_data, ErlDrvThreadData thread_data)
{
async_sqlite3_command *async_command = (async_sqlite3_command *)thread_data;
sqlite3_drv_t *drv = async_command->driver_data;
int res = driver_output_term(drv->port, async_command->dataset, async_command->term_count);
// fprintf(drv->log, "Total term count: %p %d, rows count: %d (%d)\n", async_command->statement, async_command->term_count, async_command->row_count, res);
// fflush (drv->log);
sql_free_async(async_command);
}
// Unkown Command
static int unknown(sqlite3_drv_t *drv, char *command, int command_size) {
// Return {error, unkown_command}
ErlDrvTermData spec[] = {ERL_DRV_ATOM, drv->atom_error,
ERL_DRV_ATOM, drv->atom_unknown_cmd,
ERL_DRV_TUPLE, 2};
return driver_output_term(drv->port, spec, sizeof(spec) / sizeof(spec[0]));
}
测试输出：
module 'sqlite3_test'
sqlite3_test: basic_functionality_test...Dataset element: 1
Dataset element: 20
Dataset element: 2000
Dataset element: 2
Dataset element: 30
Dataset element: 2000
*failed*
::error:{assertEqual_failed,
[{module,sqlite3_test},
{line,58},
{expression,"sqlite3 : sql_exec ( ct , \"select * from user;\" )"},
{expected,
[{columns,["id","name","age","wage"]},
{rows,[{1,<<"abby">>,20,2000},{2,<<"marge">>,30,2000}]}]},
{value,
[{columns,["id","name","age","wage"]},
{rows,[{0,<<"abby">>,20,2000},{2,<<"marge">>,30,2000}]}]}]}
in function sqlite3_test:'-basic_functionality_test/0-fun-5-'/1
in call from sqlite3_test:basic_functionality_test/0
sqlite3_test: large_number_test...Dataset element: 4294967298
Dataset element: 4294967298
*failed*
::error:{assertEqual_failed,
[{module,sqlite3_test},
{line,141},
{expression,"rows ( sqlite3 : sql_exec ( ct , Query1 ) )"},
{expected,[{4294967298,4294967298}]},
{value,[{4294967296,4294967298}]}]}
in function sqlite3_test:'-large_number_test/0-fun-0-'/2
因此，当第一个列是一个整数时，正确的值将被放入数据集中，但Erlang会从驱动程序中获得不同的值。为什么会发生这种情况？
答案 0 :(得分：0)
由于重新分配数组而导致问题发生。当我打印int64 s的地址及其值时，我的输出类似于
While filling row: (0x8a9c010:4294967298 )
dataset (22 terms):
int64: 0x8a9c010:4294967298
While filling row: (0x8a9bfb8:4294967298 0x8a9bfc0:4294967298 )
dataset (24 terms):
int64: 0x8a9c010:4294967296
int64: 0x8a9bfc0:4294967298
While filling row: (0x8a9bfb8:4294967298 0x8a9bfc0:4294967298 0x8a9bfc8:4294967298 )
dataset (26 terms):
int64: 0x8a9c010:4294967296
int64: 0x8a9bfc0:4294967298
int64: 0x8a9bfc8:4294967298
（数组int64s在“填充行”后的括号中打印，下面的值取自数据集）。因此，当重新分配数组时，数据集中列出的指针指向旧数组。
通过切换到链接列表来修复。