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 <stdint.h>
   9 #include <string>
  10 #include <vector>
  11
  12 #include "base/macros.h"
  13 #include "base/memory/ref_counted.h"
  14 #include "base/strings/string16.h"
  15 #include "sql/connection.h"
  16 #include "sql/sql_export.h"
  17
  18 namespace sql {
  19
  20 // Possible return values from ColumnType in a statement. These should match
  21 // the values in sqlite3.h.
  22 enum ColType {
  23   COLUMN_TYPE_INTEGER = 1,
  24   COLUMN_TYPE_FLOAT = 2,
  25   COLUMN_TYPE_TEXT = 3,
  26   COLUMN_TYPE_BLOB = 4,
  27   COLUMN_TYPE_NULL = 5,
  28 };
  29
  30 // Normal usage:
  31 //   sql::Statement s(connection_.GetUniqueStatement(...));
  32 //   s.BindInt(0, a);
  33 //   if (s.Step())
  34 //     return s.ColumnString(0);
  35 //
  36 //   If there are errors getting the statement, the statement will be inert; no
  37 //   mutating or database-access methods will work. If you need to check for
  38 //   validity, use:
  39 //   if (!s.is_valid())
  40 //     return false;
  41 //
  42 // Step() and Run() just return true to signal success. If you want to handle
  43 // specific errors such as database corruption, install an error handler in
  44 // in the connection object using set_error_delegate().
  45 class SQL_EXPORT Statement {
  46  public:
  47   // Creates an uninitialized statement. The statement will be invalid until
  48   // you initialize it via Assign.
  49   Statement();
  50
  51   explicit Statement(scoped_refptr<Connection::StatementRef> ref);
  52   ~Statement();
  53
  54   // Initializes this object with the given statement, which may or may not
  55   // be valid. Use is_valid() to check if it's OK.
  56   void Assign(scoped_refptr<Connection::StatementRef> ref);
  57
  58   // Resets the statement to an uninitialized state corrosponding to
  59   // the default constructor, releasing the StatementRef.
  60   void Clear();
  61
  62   // Returns true if the statement can be executed. All functions can still
  63   // be used if the statement is invalid, but they will return failure or some
  64   // default value. This is because the statement can become invalid in the
  65   // middle of executing a command if there is a serious error and the database
  66   // has to be reset.
  67   bool is_valid() const { return ref_->is_valid(); }
  68
  69   // Running -------------------------------------------------------------------
  70
  71   // Executes the statement, returning true on success. This is like Step but
  72   // for when there is no output, like an INSERT statement.
  73   bool Run();
  74
  75   // Executes the statement, returning true if there is a row of data returned.
  76   // You can keep calling Step() until it returns false to iterate through all
  77   // the rows in your result set.
  78   //
  79   // When Step returns false, the result is either that there is no more data
  80   // or there is an error. This makes it most convenient for loop usage. If you
  81   // need to disambiguate these cases, use Succeeded().
  82   //
  83   // Typical example:
  84   //   while (s.Step()) {
  85   //     ...
  86   //   }
  87   //   return s.Succeeded();
  88   bool Step();
  89
  90   // Resets the statement to its initial condition. This includes any current
  91   // result row, and also the bound variables if the |clear_bound_vars| is true.
  92   void Reset(bool clear_bound_vars);
  93
  94   // Returns true if the last executed thing in this statement succeeded. If
  95   // there was no last executed thing or the statement is invalid, this will
  96   // return false.
  97   bool Succeeded() const;
  98
  99   // Binding -------------------------------------------------------------------
 100
 101   // These all take a 0-based argument index and return true on success. You
 102   // may not always care about the return value (they'll DCHECK if they fail).
 103   // The main thing you may want to check is when binding large blobs or
 104   // strings there may be out of memory.
 105   bool BindNull(int col);
 106   bool BindBool(int col, bool val);
 107   bool BindInt(int col, int val);
 108   bool BindInt64(int col, int64_t val);
 109   bool BindDouble(int col, double val);
 110   bool BindCString(int col, const char* val);
 111   bool BindString(int col, const std::string& val);
 112   bool BindString16(int col, const base::string16& value);
 113   bool BindBlob(int col, const void* value, int value_len);
 114
 115   // Retrieving ----------------------------------------------------------------
 116
 117   // Returns the number of output columns in the result.
 118   int ColumnCount() const;
 119
 120   // Returns the type associated with the given column.
 121   //
 122   // Watch out: the type may be undefined if you've done something to cause a
 123   // "type conversion." This means requesting the value of a column of a type
 124   // where that type is not the native type. For safety, call ColumnType only
 125   // on a column before getting the value out in any way.
 126   ColType ColumnType(int col) const;
 127   ColType DeclaredColumnType(int col) const;
 128
 129   // These all take a 0-based argument index.
 130   bool ColumnBool(int col) const;
 131   int ColumnInt(int col) const;
 132   int64_t ColumnInt64(int col) const;
 133   double ColumnDouble(int col) const;
 134   std::string ColumnString(int col) const;
 135   base::string16 ColumnString16(int col) const;
 136
 137   // When reading a blob, you can get a raw pointer to the underlying data,
 138   // along with the length, or you can just ask us to copy the blob into a
 139   // vector. Danger! ColumnBlob may return NULL if there is no data!
 140   int ColumnByteLength(int col) const;
 141   const void* ColumnBlob(int col) const;
 142   bool ColumnBlobAsString(int col, std::string* blob);
 143   bool ColumnBlobAsString16(int col, base::string16* val) const;
 144   bool ColumnBlobAsVector(int col, std::vector<char>* val) const;
 145   bool ColumnBlobAsVector(int col, std::vector<unsigned char>* val) const;
 146
 147   // Diagnostics --------------------------------------------------------------
 148
 149   // Returns the original text of sql statement. Do not keep a pointer to it.
 150   const char* GetSQLStatement();
 151
 152  private:
 153   // This is intended to check for serious errors and report them to the
 154   // connection object. It takes a sqlite error code, and returns the same
 155   // code. Currently this function just updates the succeeded flag, but will be
 156   // enhanced in the future to do the notification.
 157   int CheckError(int err);
 158
 159   // Contraction for checking an error code against SQLITE_OK. Does not set the
 160   // succeeded flag.
 161   bool CheckOk(int err) const;
 162
 163   // Should be called by all mutating methods to check that the statement is
 164   // valid. Returns true if the statement is valid. DCHECKS and returns false
 165   // if it is not.
 166   // The reason for this is to handle two specific cases in which a Statement
 167   // may be invalid. The first case is that the programmer made an SQL error.
 168   // Those cases need to be DCHECKed so that we are guaranteed to find them
 169   // before release. The second case is that the computer has an error (probably
 170   // out of disk space) which is prohibiting the correct operation of the
 171   // database. Our testing apparatus should not exhibit this defect, but release
 172   // situations may. Therefore, the code is handling disjoint situations in
 173   // release and test. In test, we're ensuring correct SQL. In release, we're
 174   // ensuring that contracts are honored in error edge cases.
 175   bool CheckValid() const;
 176
 177   // The actual sqlite statement. This may be unique to us, or it may be cached
 178   // by the connection, which is why it's refcounted. This pointer is
 179   // guaranteed non-NULL.
 180   scoped_refptr<Connection::StatementRef> ref_;
 181
 182   // Set after Step() or Run() are called, reset by Reset().  Used to
 183   // prevent accidental calls to API functions which would not work
 184   // correctly after stepping has started.
 185   bool stepped_;
 186
 187   // See Succeeded() for what this holds.
 188   bool succeeded_;
 189
 190   DISALLOW_COPY_AND_ASSIGN(Statement);
 191 };
 192
 193 }  // namespace sql
 194
 195 #endif  // SQL_STATEMENT_H_