root/src/common/sql.c

// Copyright (c) Athena Dev Teams - Licensed under GNU GPL
// For more information, see LICENCE in the main folder

#include "../common/cbasetypes.h"
#include "../common/malloc.h"
#include "../common/showmsg.h"
#include "../common/strlib.h"
#include "sql.h"

#ifdef WIN32
#include <winsock2.h>
#endif
#include <mysql.h>
#include <string.h>// strlen/strnlen/memcpy/memset
#include <stdlib.h>// strtoul



/// Sql handle
struct Sql
{
        StringBuf buf;
        MYSQL handle;
        MYSQL_RES* result;
        MYSQL_ROW row;
        unsigned long* lengths;
};



// Column length receiver.
// Takes care of the possible size missmatch between uint32 and unsigned long.
struct s_column_length
{
        uint32* out_length;
        unsigned long length;
};
typedef struct s_column_length s_column_length;



/// Sql statement
struct SqlStmt
{
        StringBuf buf;
        MYSQL_STMT* stmt;
        MYSQL_BIND* params;
        MYSQL_BIND* columns;
        s_column_length* column_lengths;
        size_t max_params;
        size_t max_columns;
        bool bind_params;
        bool bind_columns;
};



///////////////////////////////////////////////////////////////////////////////
// Sql Handle
///////////////////////////////////////////////////////////////////////////////



/// Allocates and initializes a new Sql handle.
Sql* Sql_Malloc(void)
{
        Sql* self;
        CREATE(self, Sql, 1);
        mysql_init(&self->handle);
        StringBuf_Init(&self->buf);
        return self;
}



/// Establishes a connection.
int Sql_Connect(Sql* self, const char* user, const char* passwd, const char* host, uint16 port, const char* db)
{
        if( self == NULL )
                return SQL_ERROR;

        StringBuf_Clear(&self->buf);
        if( !mysql_real_connect(&self->handle, host, user, passwd, db, (unsigned int)port, NULL/*unix_socket*/, 0/*clientflag*/) )
        {
                ShowSQL("%s\n", mysql_error(&self->handle));
                return SQL_ERROR;
        }
        return SQL_SUCCESS;
}



/// Retrieves the timeout of the connection.
int Sql_GetTimeout(Sql* self, uint32* out_timeout)
{
        if( self && out_timeout && SQL_SUCCESS == Sql_Query(self, "SHOW VARIABLES LIKE 'wait_timeout'") )
        {
                char* data;
                size_t len;
                if( SQL_SUCCESS == Sql_NextRow(self) &&
                        SQL_SUCCESS == Sql_GetData(self, 1, &data, &len) )
                {
                        *out_timeout = (uint32)strtoul(data, NULL, 10);
                        Sql_FreeResult(self);
                        return SQL_SUCCESS;
                }
                Sql_FreeResult(self);
        }
        return SQL_ERROR;
}



/// Retrieves the name of the columns of a table into out_buf, with the separator after each name.
int Sql_GetColumnNames(Sql* self, const char* table, char* out_buf, size_t buf_len, char sep)
{
        char* data;
        size_t len;
        size_t off = 0;

        if( self == NULL || SQL_ERROR == Sql_Query(self, "EXPLAIN `%s`", table) )
                return SQL_ERROR;

        out_buf[off] = '\0';
        while( SQL_SUCCESS == Sql_NextRow(self) && SQL_SUCCESS == Sql_GetData(self, 0, &data, &len) )
        {
                len = strnlen(data, len);
                if( off + len + 2 > buf_len )
                {
                        ShowDebug("Sql_GetColumns: output buffer is too small\n");
                        *out_buf = '\0';
                        return SQL_ERROR;
                }
                memcpy(out_buf+off, data, len);
                off += len;
                out_buf[off++] = sep;
        }
        out_buf[off] = '\0';
        Sql_FreeResult(self);
        return SQL_SUCCESS;
}



/// Changes the encoding of the connection.
int Sql_SetEncoding(Sql* self, const char* encoding)
{
        if( self && mysql_set_character_set(&self->handle, encoding) )
                return SQL_SUCCESS;
        return SQL_ERROR;
}



/// Pings the connection.
int Sql_Ping(Sql* self)
{
        if( self && mysql_ping(&self->handle) == 0 )
                return SQL_SUCCESS;
        return SQL_ERROR;
}



/// Escapes a string.
size_t Sql_EscapeString(Sql* self, char *out_to, const char *from)
{
        if( self )
                return (size_t)mysql_real_escape_string(&self->handle, out_to, from, (unsigned long)strlen(from));
        else
                return (size_t)mysql_escape_string(out_to, from, (unsigned long)strlen(from));
}



/// Escapes a string.
size_t Sql_EscapeStringLen(Sql* self, char *out_to, const char *from, size_t from_len)
{
        if( self )
                return (size_t)mysql_real_escape_string(&self->handle, out_to, from, (unsigned long)from_len);
        else
                return (size_t)mysql_escape_string(out_to, from, (unsigned long)from_len);
}



/// Executes a query.
int Sql_Query(Sql* self, const char* query, ...)
{
        int res;
        va_list args;

        va_start(args, query);
        res = Sql_QueryV(self, query, args);
        va_end(args);

        return res;
}



/// Executes a query.
int Sql_QueryV(Sql* self, const char* query, va_list args)
{
        if( self == NULL )
                return SQL_ERROR;

        Sql_FreeResult(self);
        StringBuf_Clear(&self->buf);
        StringBuf_Vprintf(&self->buf, query, args);
        if( mysql_real_query(&self->handle, StringBuf_Value(&self->buf), (unsigned long)StringBuf_Length(&self->buf)) )
        {
                ShowSQL("DB error - %s\n", mysql_error(&self->handle));
                return SQL_ERROR;
        }
        self->result = mysql_store_result(&self->handle);
        if( mysql_errno(&self->handle) != 0 )
        {
                ShowSQL("DB error - %s\n", mysql_error(&self->handle));
                return SQL_ERROR;
        }
        return SQL_SUCCESS;
}



/// Executes a query.
int Sql_QueryStr(Sql* self, const char* query)
{
        if( self == NULL )
                return SQL_ERROR;

        Sql_FreeResult(self);
        StringBuf_Clear(&self->buf);
        StringBuf_AppendStr(&self->buf, query);
        if( mysql_real_query(&self->handle, StringBuf_Value(&self->buf), (unsigned long)StringBuf_Length(&self->buf)) )
        {
                ShowSQL("DB error - %s\n", mysql_error(&self->handle));
                return SQL_ERROR;
        }
        self->result = mysql_store_result(&self->handle);
        if( mysql_errno(&self->handle) != 0 )
        {
                ShowSQL("DB error - %s\n", mysql_error(&self->handle));
                return SQL_ERROR;
        }
        return SQL_SUCCESS;
}



/// Returns the number of the AUTO_INCREMENT column of the last INSERT/UPDATE query.
uint64 Sql_LastInsertId(Sql* self)
{
        if( self )
                return (uint64)mysql_insert_id(&self->handle);
        else
                return 0;
}



/// Returns the number of columns in each row of the result.
uint32 Sql_NumColumns(Sql* self)
{
        if( self && self->result )
                return (uint32)mysql_num_fields(self->result);
        return 0;
}



/// Returns the number of rows in the result.
uint64 Sql_NumRows(Sql* self)
{
        if( self && self->result )
                return (uint64)mysql_num_rows(self->result);
        return 0;
}



/// Fetches the next row.
int Sql_NextRow(Sql* self)
{
        if( self && self->result )
        {
                self->row = mysql_fetch_row(self->result);
                if( self->row )
                {
                        self->lengths = mysql_fetch_lengths(self->result);
                        return SQL_SUCCESS;
                }
                self->lengths = NULL;
                if( mysql_errno(&self->handle) == 0 )
                        return SQL_NO_DATA;
        }
        return SQL_ERROR;
}



/// Gets the data of a column.
int Sql_GetData(Sql* self, size_t col, char** out_buf, size_t* out_len)
{
        if( self && self->row )
        {
                if( col < Sql_NumColumns(self) )
                {
                        if( out_buf ) *out_buf = self->row[col];
                        if( out_len ) *out_len = (size_t)self->lengths[col];
                }
                else
                {// out of range - ignore
                        if( out_buf ) *out_buf = NULL;
                        if( out_len ) *out_len = 0;
                }
                return SQL_SUCCESS;
        }
        return SQL_ERROR;
}



/// Frees the result of the query.
void Sql_FreeResult(Sql* self)
{
        if( self && self->result )
        {
                mysql_free_result(self->result);
                self->result = NULL;
                self->row = NULL;
                self->lengths = NULL;
        }
}



/// Shows debug information (last query).
void Sql_ShowDebug_(Sql* self, const char* debug_file, const unsigned long debug_line)
{
        if( self == NULL )
                ShowDebug("at %s:%lu - self is NULL\n", debug_file, debug_line);
        else if( StringBuf_Length(&self->buf) > 0 )
                ShowDebug("at %s:%lu - %s\n", debug_file, debug_line, StringBuf_Value(&self->buf));
        else
                ShowDebug("at %s:%lu\n", debug_file, debug_line);
}



/// Frees a Sql handle returned by Sql_Malloc.
void Sql_Free(Sql* self) 
{
        if( self )
        {
                Sql_FreeResult(self);
                StringBuf_Destroy(&self->buf);
                aFree(self);
        }
}



///////////////////////////////////////////////////////////////////////////////
// Prepared Statements
///////////////////////////////////////////////////////////////////////////////



/// Returns the mysql integer type for the target size.
///
/// @private
static enum enum_field_types Sql_P_SizeToMysqlIntType(int sz)
{
        switch( sz )
        {
        case 1: return MYSQL_TYPE_TINY;
        case 2: return MYSQL_TYPE_SHORT;
        case 4: return MYSQL_TYPE_LONG;
        case 8: return MYSQL_TYPE_LONGLONG;
        default:
                ShowDebug("SizeToMysqlIntType: unsupported size (%d)\n", sz);
                return MYSQL_TYPE_NULL;
        }
}



/// Binds a parameter/result.
///
/// @private
static int Sql_P_BindSqlDataType(MYSQL_BIND* bind, enum SqlDataType buffer_type, void* buffer, size_t buffer_len, unsigned long* out_length, int8* out_is_null)
{
        memset(bind, 0, sizeof(MYSQL_BIND));
        switch( buffer_type )
        {
        case SQLDT_NULL: bind->buffer_type = MYSQL_TYPE_NULL;
                buffer_len = 0;// FIXME length = ? [FlavioJS]
                break;
        // fixed size
        case SQLDT_UINT8: bind->is_unsigned = 1;
        case SQLDT_INT8: bind->buffer_type = MYSQL_TYPE_TINY;
                buffer_len = 1;
                break;
        case SQLDT_UINT16: bind->is_unsigned = 1;
        case SQLDT_INT16: bind->buffer_type = MYSQL_TYPE_SHORT;
                buffer_len = 2;
                break;
        case SQLDT_UINT32: bind->is_unsigned = 1;
        case SQLDT_INT32: bind->buffer_type = MYSQL_TYPE_LONG;
                buffer_len = 4;
                break;
        case SQLDT_UINT64: bind->is_unsigned = 1;
        case SQLDT_INT64: bind->buffer_type = MYSQL_TYPE_LONGLONG;
                buffer_len = 8;
                break;
        // platform dependent size
        case SQLDT_UCHAR: bind->is_unsigned = 1;
        case SQLDT_CHAR: bind->buffer_type = Sql_P_SizeToMysqlIntType(sizeof(char));
                buffer_len = sizeof(char);
                break;
        case SQLDT_USHORT: bind->is_unsigned = 1;
        case SQLDT_SHORT: bind->buffer_type = Sql_P_SizeToMysqlIntType(sizeof(short));
                buffer_len = sizeof(short);
                break;
        case SQLDT_UINT: bind->is_unsigned = 1;
        case SQLDT_INT: bind->buffer_type = Sql_P_SizeToMysqlIntType(sizeof(int));
                buffer_len = sizeof(int);
                break;
        case SQLDT_ULONG: bind->is_unsigned = 1;
        case SQLDT_LONG: bind->buffer_type = Sql_P_SizeToMysqlIntType(sizeof(long));
                buffer_len = sizeof(long);
                break;
        case SQLDT_ULONGLONG: bind->is_unsigned = 1;
        case SQLDT_LONGLONG: bind->buffer_type = Sql_P_SizeToMysqlIntType(sizeof(long long));
                buffer_len = sizeof(long long);
                break;
        // floating point
        case SQLDT_FLOAT: bind->buffer_type = MYSQL_TYPE_FLOAT;
                buffer_len = 4;
                break;
        case SQLDT_DOUBLE: bind->buffer_type = MYSQL_TYPE_DOUBLE;
                buffer_len = 8;
                break;
        // other
        case SQLDT_STRING:
        case SQLDT_ENUM: bind->buffer_type = MYSQL_TYPE_STRING;
                break;
        case SQLDT_BLOB: bind->buffer_type = MYSQL_TYPE_BLOB;
                break;
        default:
                ShowDebug("Sql_P_BindSqlDataType: unsupported buffer type (%d)\n", buffer_type);
                return SQL_ERROR;
        }
        bind->buffer = buffer;
        bind->buffer_length = (unsigned long)buffer_len;
        bind->length = out_length;
        bind->is_null = (my_bool*)out_is_null;
        return SQL_SUCCESS;
}



/// Prints debug information about a field (type and length).
///
/// @private
static void Sql_P_ShowDebugMysqlFieldInfo(const char* prefix, enum enum_field_types type, int is_unsigned, unsigned long length, const char* length_postfix)
{
        const char* sign = (is_unsigned ? "UNSIGNED " : "");
        const char* type_string;
        switch( type )
        {
        default:
                ShowDebug("%stype=%s%u, length=%d\n", prefix, sign, type, length);
                return;
#define SHOW_DEBUG_OF(x) case x: type_string = #x; break
        SHOW_DEBUG_OF(MYSQL_TYPE_TINY);
        SHOW_DEBUG_OF(MYSQL_TYPE_SHORT);
        SHOW_DEBUG_OF(MYSQL_TYPE_LONG);
        SHOW_DEBUG_OF(MYSQL_TYPE_INT24);
        SHOW_DEBUG_OF(MYSQL_TYPE_LONGLONG);
        SHOW_DEBUG_OF(MYSQL_TYPE_DECIMAL);
        SHOW_DEBUG_OF(MYSQL_TYPE_FLOAT);
        SHOW_DEBUG_OF(MYSQL_TYPE_DOUBLE);
        SHOW_DEBUG_OF(MYSQL_TYPE_TIMESTAMP);
        SHOW_DEBUG_OF(MYSQL_TYPE_DATE);
        SHOW_DEBUG_OF(MYSQL_TYPE_TIME);
        SHOW_DEBUG_OF(MYSQL_TYPE_DATETIME);
        SHOW_DEBUG_OF(MYSQL_TYPE_YEAR);
        SHOW_DEBUG_OF(MYSQL_TYPE_STRING);
        SHOW_DEBUG_OF(MYSQL_TYPE_VAR_STRING);
        SHOW_DEBUG_OF(MYSQL_TYPE_BLOB);
        SHOW_DEBUG_OF(MYSQL_TYPE_SET);
        SHOW_DEBUG_OF(MYSQL_TYPE_ENUM);
        SHOW_DEBUG_OF(MYSQL_TYPE_NULL);
#undef SHOW_DEBUG_TYPE_OF
        }
        ShowDebug("%stype=%s%s, length=%d%s\n", prefix, sign, type_string, length, length_postfix); 
}



/// Reports debug information about a truncated column.
///
/// @private
static void SqlStmt_P_ShowDebugTruncatedColumn(SqlStmt* self, size_t i)
{
        MYSQL_RES* meta;
        MYSQL_FIELD* field;
        MYSQL_BIND* column;

        meta = mysql_stmt_result_metadata(self->stmt);
        field = mysql_fetch_field_direct(meta, (unsigned int)i);
        ShowSQL("DB error - data of field '%s' was truncated.\n", field->name);
        ShowDebug("column - %lu\n", (unsigned long)i);
        Sql_P_ShowDebugMysqlFieldInfo("data   - ", field->type, field->flags&UNSIGNED_FLAG, self->column_lengths[i].length, "");
        column = &self->columns[i];
        if( column->buffer_type == MYSQL_TYPE_STRING )
                Sql_P_ShowDebugMysqlFieldInfo("buffer - ", column->buffer_type, column->is_unsigned, column->buffer_length, "+1(nul-terminator)");
        else
                Sql_P_ShowDebugMysqlFieldInfo("buffer - ", column->buffer_type, column->is_unsigned, column->buffer_length, "");
        mysql_free_result(meta);
}



/// Allocates and initializes a new SqlStmt handle.
SqlStmt* SqlStmt_Malloc(Sql* sql)
{
        SqlStmt* self;
        MYSQL_STMT* stmt;

        if( sql == NULL )
                return NULL;

        stmt = mysql_stmt_init(&sql->handle);
        if( stmt == NULL )
        {
                ShowSQL("DB error - %s\n", mysql_error(&sql->handle));
                return NULL;
        }
        CREATE(self, SqlStmt, 1);
        StringBuf_Init(&self->buf);
        self->stmt = stmt;
        self->params = NULL;
        self->columns = NULL;
        self->column_lengths = NULL;
        self->max_params = 0;
        self->max_columns = 0;
        self->bind_params = false;
        self->bind_columns = false;

        return self;
}



/// Prepares the statement.
int SqlStmt_Prepare(SqlStmt* self, const char* query, ...)
{
        int res;
        va_list args;

        va_start(args, query);
        res = SqlStmt_PrepareV(self, query, args);
        va_end(args);

        return res;
}



/// Prepares the statement.
int SqlStmt_PrepareV(SqlStmt* self, const char* query, va_list args)
{
        if( self == NULL )
                return SQL_ERROR;

        SqlStmt_FreeResult(self);
        StringBuf_Clear(&self->buf);
        StringBuf_Vprintf(&self->buf, query, args);
        if( mysql_stmt_prepare(self->stmt, StringBuf_Value(&self->buf), (unsigned long)StringBuf_Length(&self->buf)) )
        {
                ShowSQL("DB error - %s\n", mysql_stmt_error(self->stmt));
                return SQL_ERROR;
        }
        self->bind_params = false;

        return SQL_SUCCESS;
}



/// Prepares the statement.
int SqlStmt_PrepareStr(SqlStmt* self, const char* query)
{
        if( self == NULL )
                return SQL_ERROR;

        SqlStmt_FreeResult(self);
        StringBuf_Clear(&self->buf);
        StringBuf_AppendStr(&self->buf, query);
        if( mysql_stmt_prepare(self->stmt, StringBuf_Value(&self->buf), (unsigned long)StringBuf_Length(&self->buf)) )
        {
                ShowSQL("DB error - %s\n", mysql_stmt_error(self->stmt));
                return SQL_ERROR;
        }
        self->bind_params = false;

        return SQL_SUCCESS;
}



/// Returns the number of parameters in the prepared statement.
size_t SqlStmt_NumParams(SqlStmt* self)
{
        if( self )
                return (size_t)mysql_stmt_param_count(self->stmt);
        else
                return 0;
}



/// Binds a parameter to a buffer.
int SqlStmt_BindParam(SqlStmt* self, size_t idx, enum SqlDataType buffer_type, void* buffer, size_t buffer_len)
{
        if( self == NULL )
                return SQL_ERROR;

        if( !self->bind_params )
        {// initialize the bindings
                size_t i;
                size_t count;

                count = SqlStmt_NumParams(self);
                if( self->max_params < count )
                {
                        self->max_params = count;
                        RECREATE(self->params, MYSQL_BIND, count);
                }
                memset(self->params, 0, count*sizeof(MYSQL_BIND));
                for( i = 0; i < count; ++i )
                        self->params[i].buffer_type = MYSQL_TYPE_NULL;
                self->bind_params = true;
        }
        if( idx < self->max_params )
                return Sql_P_BindSqlDataType(self->params+idx, buffer_type, buffer, buffer_len, NULL, NULL);
        else
                return SQL_SUCCESS;// out of range - ignore
}



/// Executes the prepared statement.
int SqlStmt_Execute(SqlStmt* self)
{
        if( self == NULL )
                return SQL_ERROR;

        SqlStmt_FreeResult(self);
        if( (self->bind_params && mysql_stmt_bind_param(self->stmt, self->params)) ||
                mysql_stmt_execute(self->stmt) )
        {
                ShowSQL("DB error - %s\n", mysql_stmt_error(self->stmt));
                return SQL_ERROR;
        }
        self->bind_columns = false;
        if( mysql_stmt_store_result(self->stmt) )// store all the data
        {
                ShowSQL("DB error - %s\n", mysql_stmt_error(self->stmt));
                return SQL_ERROR;
        }

        return SQL_SUCCESS;
}



/// Returns the number of the AUTO_INCREMENT column of the last INSERT/UPDATE statement.
uint64 SqlStmt_LastInsertId(SqlStmt* self)
{
        if( self )
                return (uint64)mysql_stmt_insert_id(self->stmt);
        else
                return 0;
}



/// Returns the number of columns in each row of the result.
size_t SqlStmt_NumColumns(SqlStmt* self)
{
        if( self )
                return (size_t)mysql_stmt_field_count(self->stmt);
        else
                return 0;
}



/// Binds the result of a column to a buffer.
int SqlStmt_BindColumn(SqlStmt* self, size_t idx, enum SqlDataType buffer_type, void* buffer, size_t buffer_len, uint32* out_length, int8* out_is_null)
{
        if( self == NULL )
                return SQL_ERROR;

        if( buffer_type == SQLDT_STRING || buffer_type == SQLDT_ENUM )
        {
                if( buffer_len < 1 )
                {
                        ShowDebug("SqlStmt_BindColumn: buffer_len(%d) is too small, no room for the nul-terminator\n", buffer_len);
                        return SQL_ERROR;
                }
                --buffer_len;// nul-terminator
        }
        if( !self->bind_columns )
        {// initialize the bindings
                size_t i;
                size_t cols;

                cols = SqlStmt_NumColumns(self);
                if( self->max_columns < cols )
                {
                        self->max_columns = cols;
                        RECREATE(self->columns, MYSQL_BIND, cols);
                        RECREATE(self->column_lengths, s_column_length, cols);
                }
                memset(self->columns, 0, cols*sizeof(MYSQL_BIND));
                memset(self->column_lengths, 0, cols*sizeof(s_column_length));
                for( i = 0; i < cols; ++i )
                        self->columns[i].buffer_type = MYSQL_TYPE_NULL;
                self->bind_columns = true;
        }
        if( idx < self->max_columns )
        {
                self->column_lengths[idx].out_length = out_length;
                return Sql_P_BindSqlDataType(self->columns+idx, buffer_type, buffer, buffer_len, &self->column_lengths[idx].length, out_is_null);
        }
        else
        {
                return SQL_SUCCESS;// out of range - ignore
        }
}



/// Returns the number of rows in the result.
uint64 SqlStmt_NumRows(SqlStmt* self)
{
        if( self )
                return (uint64)mysql_stmt_num_rows(self->stmt);
        else
                return 0;
}



/// Fetches the next row.
int SqlStmt_NextRow(SqlStmt* self)
{
        int err;
        size_t i;
        size_t cols;
        MYSQL_BIND* column;
        unsigned long length;

        if( self == NULL )
                return SQL_ERROR;

        // bind columns
        if( self->bind_columns && mysql_stmt_bind_result(self->stmt, self->columns) )
                err = 1;// error binding columns
        else
                err = mysql_stmt_fetch(self->stmt);// fetch row

        // check for errors
        if( err == MYSQL_NO_DATA )
                return SQL_NO_DATA;
#if defined(MYSQL_DATA_TRUNCATED)
        // MySQL 5.0/5.1 defines and returns MYSQL_DATA_TRUNCATED [FlavioJS]
        if( err == MYSQL_DATA_TRUNCATED )
        {
                my_bool truncated;

                if( !self->bind_columns )
                {
                        ShowSQL("DB error - data truncated (unknown source, columns are not bound)\n");
                        return SQL_ERROR;
                }

                // find truncated column
                cols = SqlStmt_NumColumns(self);
                for( i = 0; i < cols; ++i )
                {
                        column = &self->columns[i];
                        column->error = &truncated;
                        mysql_stmt_fetch_column(self->stmt, column, (unsigned int)i, 0);
                        column->error = NULL;
                        if( truncated )
                        {// report truncated column
                                SqlStmt_P_ShowDebugTruncatedColumn(self, i);
                                return SQL_ERROR;
                        }
                }
                ShowSQL("DB error - data truncated (unknown source)\n");
                return SQL_ERROR;
        }
#endif
        if( err )
        {
                ShowSQL("DB error - %s\n", mysql_stmt_error(self->stmt));
                return SQL_ERROR;
        }

        // propagate column lengths and clear unused parts of string/enum/blob buffers
        cols = SqlStmt_NumColumns(self);
        for( i = 0; i < cols; ++i )
        {
                length = self->column_lengths[i].length;
                column = &self->columns[i];
#if !defined(MYSQL_DATA_TRUNCATED)
                // MySQL 4.1/(below?) returns success even if data is truncated, so we test truncation manually [FlavioJS]
                if( column->buffer_length < length )
                {// report truncated column
                        if( column->buffer_type == MYSQL_TYPE_STRING || column->buffer_type == MYSQL_TYPE_BLOB )
                        {// string/enum/blob column
                                SqlStmt_P_ShowDebugTruncatedColumn(self, i);
                                return SQL_ERROR;
                        }
                        // FIXME numeric types and null [FlavioJS]
                }
#endif
                if( self->column_lengths[i].out_length )
                        *self->column_lengths[i].out_length = (uint32)length;
                if( column->buffer_type == MYSQL_TYPE_STRING )
                {// clear unused part of the string/enum buffer (and nul-terminate)
                        memset((char*)column->buffer + length, 0, column->buffer_length - length + 1);
                }
                else if( column->buffer_type == MYSQL_TYPE_BLOB && length < column->buffer_length )
                {// clear unused part of the blob buffer
                        memset((char*)column->buffer + length, 0, column->buffer_length - length);
                }
        }

        return SQL_SUCCESS;
}



/// Frees the result of the statement execution.
void SqlStmt_FreeResult(SqlStmt* self)
{
        if( self )
                mysql_stmt_free_result(self->stmt);
}



/// Shows debug information (with statement).
void SqlStmt_ShowDebug_(SqlStmt* self, const char* debug_file, const unsigned long debug_line)
{
        if( self == NULL )
                ShowDebug("at %s:%lu -  self is NULL\n", debug_file, debug_line);
        if( StringBuf_Length(&self->buf) > 0 )
                ShowDebug("at %s:%lu - %s\n", debug_file, debug_line, StringBuf_Value(&self->buf));
        else
                ShowDebug("at %s:%lu\n", debug_file, debug_line);
}



/// Frees a SqlStmt returned by SqlStmt_Malloc.
void SqlStmt_Free(SqlStmt* self)
{
        if( self )
        {
                SqlStmt_FreeResult(self);
                StringBuf_Destroy(&self->buf);
                mysql_stmt_close(self->stmt);
                if( self->params )
                        aFree(self->params);
                if( self->columns )
                {
                        aFree(self->columns);
                        aFree(self->column_lengths);
                }
                aFree(self);
        }
}