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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef SQL_STATEMENT_H_
#define SQL_STATEMENT_H_
#pragma once
#include <string>
#include <vector>
#include "base/basictypes.h"
#include "base/memory/ref_counted.h"
#include "base/string16.h"
#include "sql/connection.h"
#include "sql/sql_export.h"
namespace sql {
// Possible return values from ColumnType in a statement. These should match
// the values in sqlite3.h.
enum ColType {
COLUMN_TYPE_INTEGER = 1,
COLUMN_TYPE_FLOAT = 2,
COLUMN_TYPE_TEXT = 3,
COLUMN_TYPE_BLOB = 4,
COLUMN_TYPE_NULL = 5,
};
// Normal usage:
// sql::Statement s(connection_.GetUniqueStatement(...));
// s.BindInt(0, a);
// if (s.Step())
// return s.ColumnString(0);
//
// If there are errors getting the statement, the statement will be inert; no
// mutating or database-access methods will work. If you need to check for
// validity, use:
// if (!s.is_valid())
// return false;
//
// Step() and Run() just return true to signal success. If you want to handle
// specific errors such as database corruption, install an error handler in
// in the connection object using set_error_delegate().
class SQL_EXPORT Statement {
public:
// Creates an uninitialized statement. The statement will be invalid until
// you initialize it via Assign.
Statement();
explicit Statement(scoped_refptr<Connection::StatementRef> ref);
~Statement();
// Initializes this object with the given statement, which may or may not
// be valid. Use is_valid() to check if it's OK.
void Assign(scoped_refptr<Connection::StatementRef> ref);
// Resets the statement to an uninitialized state corrosponding to
// the default constructor, releasing the StatementRef.
void Clear();
// Returns true if the statement can be executed. All functions can still
// be used if the statement is invalid, but they will return failure or some
// default value. This is because the statement can become invalid in the
// middle of executing a command if there is a serious error and the database
// has to be reset.
bool is_valid() const { return ref_->is_valid(); }
// Running -------------------------------------------------------------------
// Executes the statement, returning true on success. This is like Step but
// for when there is no output, like an INSERT statement.
bool Run();
// Executes the statement, returning true if there is a row of data returned.
// You can keep calling Step() until it returns false to iterate through all
// the rows in your result set.
//
// When Step returns false, the result is either that there is no more data
// or there is an error. This makes it most convenient for loop usage. If you
// need to disambiguate these cases, use Succeeded().
//
// Typical example:
// while (s.Step()) {
// ...
// }
// return s.Succeeded();
bool Step();
// Resets the statement to its initial condition. This includes clearing all
// the bound variables and any current result row.
void Reset();
// Returns true if the last executed thing in this statement succeeded. If
// there was no last executed thing or the statement is invalid, this will
// return false.
bool Succeeded() const;
// Binding -------------------------------------------------------------------
// These all take a 0-based argument index and return true on success. You
// may not always care about the return value (they'll DCHECK if they fail).
// The main thing you may want to check is when binding large blobs or
// strings there may be out of memory.
bool BindNull(int col);
bool BindBool(int col, bool val);
bool BindInt(int col, int val);
bool BindInt64(int col, int64 val);
bool BindDouble(int col, double val);
bool BindCString(int col, const char* val);
bool BindString(int col, const std::string& val);
bool BindString16(int col, const string16& value);
bool BindBlob(int col, const void* value, int value_len);
// Retrieving ----------------------------------------------------------------
// Returns the number of output columns in the result.
int ColumnCount() const;
// Returns the type associated with the given column.
//
// Watch out: the type may be undefined if you've done something to cause a
// "type conversion." This means requesting the value of a column of a type
// where that type is not the native type. For safety, call ColumnType only
// on a column before getting the value out in any way.
ColType ColumnType(int col) const;
ColType DeclaredColumnType(int col) const;
// These all take a 0-based argument index.
bool ColumnBool(int col) const;
int ColumnInt(int col) const;
int64 ColumnInt64(int col) const;
double ColumnDouble(int col) const;
std::string ColumnString(int col) const;
string16 ColumnString16(int col) const;
// When reading a blob, you can get a raw pointer to the underlying data,
// along with the length, or you can just ask us to copy the blob into a
// vector. Danger! ColumnBlob may return NULL if there is no data!
int ColumnByteLength(int col) const;
const void* ColumnBlob(int col) const;
bool ColumnBlobAsString(int col, std::string* blob);
bool ColumnBlobAsString16(int col, string16* val) const;
bool ColumnBlobAsVector(int col, std::vector<char>* val) const;
bool ColumnBlobAsVector(int col, std::vector<unsigned char>* val) const;
// Diagnostics --------------------------------------------------------------
// Returns the original text of sql statement. Do not keep a pointer to it.
const char* GetSQLStatement();
private:
// This is intended to check for serious errors and report them to the
// connection object. It takes a sqlite error code, and returns the same
// code. Currently this function just updates the succeeded flag, but will be
// enhanced in the future to do the notification.
int CheckError(int err);
// Contraction for checking an error code against SQLITE_OK. Does not set the
// succeeded flag.
bool CheckOk(int err) const;
// Should be called by all mutating methods to check that the statement is
// valid. Returns true if the statement is valid. DCHECKS and returns false
// if it is not.
// The reason for this is to handle two specific cases in which a Statement
// may be invalid. The first case is that the programmer made an SQL error.
// Those cases need to be DCHECKed so that we are guaranteed to find them
// before release. The second case is that the computer has an error (probably
// out of disk space) which is prohibiting the correct operation of the
// database. Our testing apparatus should not exhibit this defect, but release
// situations may. Therefore, the code is handling disjoint situations in
// release and test. In test, we're ensuring correct SQL. In release, we're
// ensuring that contracts are honored in error edge cases.
bool CheckValid() const;
// The actual sqlite statement. This may be unique to us, or it may be cached
// by the connection, which is why it's refcounted. This pointer is
// guaranteed non-NULL.
scoped_refptr<Connection::StatementRef> ref_;
// See Succeeded() for what this holds.
bool succeeded_;
DISALLOW_COPY_AND_ASSIGN(Statement);
};
} // namespace sql
#endif // SQL_STATEMENT_H_
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