sql/statement.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef SQL_STATEMENT_H_
   6 #define SQL_STATEMENT_H_
   7
   8 #include <string>
   9 #include <vector>
  10
  11 #include "base/basictypes.h"
  12 #include "base/memory/ref_counted.h"
  13 #include "base/strings/string16.h"
  14 #include "sql/connection.h"
  15 #include "sql/sql_export.h"
  16
  17 namespace sql {
  18
  19 // Possible return values from ColumnType in a statement. These should match
  20 // the values in sqlite3.h.
  21 enum ColType {
  22   COLUMN_TYPE_INTEGER = 1,
  23   COLUMN_TYPE_FLOAT = 2,
  24   COLUMN_TYPE_TEXT = 3,
  25   COLUMN_TYPE_BLOB = 4,
  26   COLUMN_TYPE_NULL = 5,
  27 };
  28
  29 // Normal usage:
  30 //   sql::Statement s(connection_.GetUniqueStatement(...));
  31 //   s.BindInt(0, a);
  32 //   if (s.Step())
  33 //     return s.ColumnString(0);
  34 //
  35 //   If there are errors getting the statement, the statement will be inert; no
  36 //   mutating or database-access methods will work. If you need to check for
  37 //   validity, use:
  38 //   if (!s.is_valid())
  39 //     return false;
  40 //
  41 // Step() and Run() just return true to signal success. If you want to handle
  42 // specific errors such as database corruption, install an error handler in
  43 // in the connection object using set_error_delegate().
  44 class SQL_EXPORT Statement {
  45  public:
  46   // Creates an uninitialized statement. The statement will be invalid until
  47   // you initialize it via Assign.
  48   Statement();
  49
  50   explicit Statement(scoped_refptr<Connection::StatementRef> ref);
  51   ~Statement();
  52
  53   // Initializes this object with the given statement, which may or may not
  54   // be valid. Use is_valid() to check if it's OK.
  55   void Assign(scoped_refptr<Connection::StatementRef> ref);
  56
  57   // Resets the statement to an uninitialized state corrosponding to
  58   // the default constructor, releasing the StatementRef.
  59   void Clear();
  60
  61   // Returns true if the statement can be executed. All functions can still
  62   // be used if the statement is invalid, but they will return failure or some
  63   // default value. This is because the statement can become invalid in the
  64   // middle of executing a command if there is a serious error and the database
  65   // has to be reset.
  66   bool is_valid() const { return ref_->is_valid(); }
  67
  68   // Running -------------------------------------------------------------------
  69
  70   // Executes the statement, returning true on success. This is like Step but
  71   // for when there is no output, like an INSERT statement.
  72   bool Run();
  73
  74   // Executes the statement, returning true if there is a row of data returned.
  75   // You can keep calling Step() until it returns false to iterate through all
  76   // the rows in your result set.
  77   //
  78   // When Step returns false, the result is either that there is no more data
  79   // or there is an error. This makes it most convenient for loop usage. If you
  80   // need to disambiguate these cases, use Succeeded().
  81   //
  82   // Typical example:
  83   //   while (s.Step()) {
  84   //     ...
  85   //   }
  86   //   return s.Succeeded();
  87   bool Step();
  88
  89   // Resets the statement to its initial condition. This includes any current
  90   // result row, and also the bound variables if the |clear_bound_vars| is true.
  91   void Reset(bool clear_bound_vars);
  92
  93   // Returns true if the last executed thing in this statement succeeded. If
  94   // there was no last executed thing or the statement is invalid, this will
  95   // return false.
  96   bool Succeeded() const;
  97
  98   // Binding -------------------------------------------------------------------
  99
 100   // These all take a 0-based argument index and return true on success. You
 101   // may not always care about the return value (they'll DCHECK if they fail).
 102   // The main thing you may want to check is when binding large blobs or
 103   // strings there may be out of memory.
 104   bool BindNull(int col);
 105   bool BindBool(int col, bool val);
 106   bool BindInt(int col, int val);
 107   bool BindInt64(int col, int64 val);
 108   bool BindDouble(int col, double val);
 109   bool BindCString(int col, const char* val);
 110   bool BindString(int col, const std::string& val);
 111   bool BindString16(int col, const base::string16& value);
 112   bool BindBlob(int col, const void* value, int value_len);
 113
 114   // Retrieving ----------------------------------------------------------------
 115
 116   // Returns the number of output columns in the result.
 117   int ColumnCount() const;
 118
 119   // Returns the type associated with the given column.
 120   //
 121   // Watch out: the type may be undefined if you've done something to cause a
 122   // "type conversion." This means requesting the value of a column of a type
 123   // where that type is not the native type. For safety, call ColumnType only
 124   // on a column before getting the value out in any way.
 125   ColType ColumnType(int col) const;
 126   ColType DeclaredColumnType(int col) const;
 127
 128   // These all take a 0-based argument index.
 129   bool ColumnBool(int col) const;
 130   int ColumnInt(int col) const;
 131   int64 ColumnInt64(int col) const;
 132   double ColumnDouble(int col) const;
 133   std::string ColumnString(int col) const;
 134   base::string16 ColumnString16(int col) const;
 135
 136   // When reading a blob, you can get a raw pointer to the underlying data,
 137   // along with the length, or you can just ask us to copy the blob into a
 138   // vector. Danger! ColumnBlob may return NULL if there is no data!
 139   int ColumnByteLength(int col) const;
 140   const void* ColumnBlob(int col) const;
 141   bool ColumnBlobAsString(int col, std::string* blob);
 142   bool ColumnBlobAsString16(int col, base::string16* val) const;
 143   bool ColumnBlobAsVector(int col, std::vector<char>* val) const;
 144   bool ColumnBlobAsVector(int col, std::vector<unsigned char>* val) const;
 145
 146   // Diagnostics --------------------------------------------------------------
 147
 148   // Returns the original text of sql statement. Do not keep a pointer to it.
 149   const char* GetSQLStatement();
 150
 151  private:
 152   // This is intended to check for serious errors and report them to the
 153   // connection object. It takes a sqlite error code, and returns the same
 154   // code. Currently this function just updates the succeeded flag, but will be
 155   // enhanced in the future to do the notification.
 156   int CheckError(int err);
 157
 158   // Contraction for checking an error code against SQLITE_OK. Does not set the
 159   // succeeded flag.
 160   bool CheckOk(int err) const;
 161
 162   // Should be called by all mutating methods to check that the statement is
 163   // valid. Returns true if the statement is valid. DCHECKS and returns false
 164   // if it is not.
 165   // The reason for this is to handle two specific cases in which a Statement
 166   // may be invalid. The first case is that the programmer made an SQL error.
 167   // Those cases need to be DCHECKed so that we are guaranteed to find them
 168   // before release. The second case is that the computer has an error (probably
 169   // out of disk space) which is prohibiting the correct operation of the
 170   // database. Our testing apparatus should not exhibit this defect, but release
 171   // situations may. Therefore, the code is handling disjoint situations in
 172   // release and test. In test, we're ensuring correct SQL. In release, we're
 173   // ensuring that contracts are honored in error edge cases.
 174   bool CheckValid() const;
 175
 176   // The actual sqlite statement. This may be unique to us, or it may be cached
 177   // by the connection, which is why it's refcounted. This pointer is
 178   // guaranteed non-NULL.
 179   scoped_refptr<Connection::StatementRef> ref_;
 180
 181   // Set after Step() or Run() are called, reset by Reset().  Used to
 182   // prevent accidental calls to API functions which would not work
 183   // correctly after stepping has started.
 184   bool stepped_;
 185
 186   // See Succeeded() for what this holds.
 187   bool succeeded_;
 188
 189   DISALLOW_COPY_AND_ASSIGN(Statement);
 190 };
 191
 192 }  // namespace sql
 193
 194 #endif  // SQL_STATEMENT_H_