# Common Portability Library C++ API

## cpl_odbc.h

ODBC Abstraction Layer (C++).

class `CPLODBCDriverInstaller`
  #include <cpl_odbc.h>

  A class providing functions to install or remove ODBC driver.

  Public Functions

  `CPLODBCDriverInstaller`()
  int `InstallDriver`(const char *pszDriver, const char *pszPathIn, WORD fRequest = ODBC_INSTALL_COMPLETE)

    Installs ODBC driver or updates definition of already installed driver.

    Interanally, it calls ODBC’s SQLInstallDriverEx function.

    Return

      TRUE indicates success, FALSE if it fails.

    Parameters

      - `pszDriver`: - The driver definition as a list of keyword-value pairs describing the driver (See ODBC API Reference).

      - `pszPathIn`: - Full path of the target directory of the installation, or a null pointer (for unixODBC, NULL is passed).

      - `fRequest`: - The fRequest argument must contain one of the following values: ODBC_INSTALL_COMPLETE - (default) complete the installation request ODBC_INSTALL_INQUIRY - inquire about where a driver can be installed

  int `RemoveDriver`(const char *pszDriverName, int fRemoveDSN = FALSE)

    Removes or changes information about the driver from the Odbcinst.ini entry in the system information.

    Return

      The function returns TRUE if it is successful, FALSE if it fails. If no entry exists in the system information when this function is called, the function returns FALSE. In order to obtain usage count value, call GetUsageCount().

    Parameters

      - `pszDriverName`: - The name of the driver as registered in the Odbcinst.ini key of the system information.

      - `fRemoveDSN`: - TRUE: Remove DSNs associated with the driver specified in lpszDriver. FALSE: Do not remove DSNs associated with the driver specified in lpszDriver.

  inline int `GetUsageCount`() const

    The usage count of the driver after this function has been called.

  inline const char *`GetPathOut`() const

    Path of the target directory where the driver should be installed.

    For details, see ODBC API Reference and lpszPathOut parameter of SQLInstallDriverEx

  inline const char *`GetLastError`() const

    If InstallDriver returns FALSE, then GetLastError then error message can be obtained by calling this function.

    Internally, it calls ODBC’s SQLInstallerError function.

  inline DWORD `GetLastErrorCode`() const

    If InstallDriver returns FALSE, then GetLastErrorCode then error code can be obtained by calling this function.

    Internally, it calls ODBC’s SQLInstallerError function. See ODBC API Reference for possible error flags.

  Private Members

  char `m_szPathOut`[`ODBC_FILENAME_MAX`]
  char `m_szError`[`SQL_MAX_MESSAGE_LENGTH`]
  DWORD `m_nErrorCode`
  DWORD `m_nUsageCount`

class `CPLODBCSession`
  #include <cpl_odbc.h>

  A class representing an ODBC database session.

  Includes error collection services.

  Public Functions

  `CPLODBCSession`()

    Constructor.

  `~CPLODBCSession`()

    Destructor.

  int `EstablishSession`(const char *pszDSN, const char *pszUserid, const char *pszPassword)

    Connect to database and logon.

    Return

      TRUE on success or FALSE on failure. Call GetLastError() to get details on failure.

    Parameters

      - `pszDSN`: The name of the DSN being used to connect. This is not optional.

      - `pszUserid`: the userid to logon as, may be NULL if not not required, or provided by the DSN.

      - `pszPassword`: the password to logon with. May be NULL if not required or provided by the DSN.

  const char *`GetLastError`()

    Returns the last ODBC error message.

    Return

      pointer to an internal buffer with the error message in it. Do not free or alter. Will be an empty (but not NULL) string if there is no pending error info.

  int `ClearTransaction`()

    Clear transaction.

  int `BeginTransaction`()

    Begin transaction.

  int `CommitTransaction`()

    Commit transaction.

  int `RollbackTransaction`()

    Rollback transaction.

  inline int `IsInTransaction`()

    Returns whether a transaction is active.

  int `CloseSession`()

    Close session.

  int `Failed`(int, HSTMT = nullptr)

    Test if a return code indicates failure, return TRUE if that is the case.

    Also update error text.

    ODBC error messages are reported in the following format: [SQLState]ErrorMessage(NativeErrorCode)

    Multiple error messages are delimited by “,”.

  inline HDBC `GetConnection`()

    Return connection handle.

  inline HENV `GetEnvironment`()

    Return GetEnvironment handle.

  bool `ConnectToMsAccess`(const char *pszName, const char *pszDSNStringTemplate)

    Connects to a Microsoft Access database.

    Return

      TRUE on success or FALSE on failure. Errors will automatically be reported via CPLError.

    Since

      GDAL 3.2

    Parameters

      - `pszName`: The file name of the Access database to connect to. This is not optional.

      - `pszDSNStringTemplate`: optional DSN string template for Microsoft Access ODBC Driver. If not specified, then a set of known driver templates will be used automatically as a fallback. If specified, it is the caller’s responsibility to ensure that the template is correctly formatted.

  Private Members

  CPLString `m_osLastError` = {}
  HENV `m_hEnv` = nullptr
  HDBC `m_hDBC` = nullptr
  int `m_bInTransaction` = false
  int `m_bAutoCommit` = true

class `CPLODBCStatement`
  #include <cpl_odbc.h>

  Abstraction for statement, and resultset.

  Includes methods for executing an SQL statement, and for accessing the resultset from that statement. Also provides for executing other ODBC requests that produce results sets such as SQLColumns() and SQLTables() requests.

  Public Functions

  explicit `CPLODBCStatement`(CPLODBCSession*)

    Constructor.

  `~CPLODBCStatement`()

    Destructor.

  inline HSTMT `GetStatement`()

    Return statement handle.

  void `Clear`()

    Clear internal command text and result set definitions.

  void `AppendEscaped`(const char*)

    Append text to internal command.

    The passed text is appended to the internal SQL command text after escaping any special characters so it can be used as a character string in an SQL statement.

    Parameters

      - `pszText`: text to append.

  void `Append`(const char*)

    Append text to internal command.

    The passed text is appended to the internal SQL command text.

    Parameters

      - `pszText`: text to append.

  void `Append`(int)

    Append to internal command.

    The passed value is formatted and appended to the internal SQL command text.

    Parameters

      - `nValue`: value to append to the command.

  void `Append`(double)

    Append to internal command.

    The passed value is formatted and appended to the internal SQL command text.

    Parameters

      - `dfValue`: value to append to the command.

  int `Appendf`(const char*, ...)

    Append to internal command.

    The passed format is used to format other arguments and the result is appended to the internal command text. Long results may not be formatted properly, and should be appended with the direct Append() methods.

    Return

      FALSE if formatting fails due to result being too large.

    Parameters

      - `pszFormat`: printf() style format string.

  inline const char *`GetCommand`()

    Return statement string.

  int `ExecuteSQL`(const char* = nullptr)

    Execute an SQL statement.

    This method will execute the passed (or stored) SQL statement, and initialize information about the resultset if there is one. If a NULL statement is passed, the internal stored statement that has been previously set via Append() or Appendf() calls will be used.

    Return

      TRUE on success or FALSE if there is an error. Error details can be fetched with OGRODBCSession::GetLastError().

    Parameters

      - `pszStatement`: the SQL statement to execute, or NULL if the internally saved one should be used.

  int `Fetch`(int nOrientation = SQL_FETCH_NEXT, int nOffset = 0)

    Fetch a new record.

    Requests the next row in the current resultset using the SQLFetchScroll() call. Note that many ODBC drivers only support the default forward fetching one record at a time. Only SQL_FETCH_NEXT (the default) should be considered reliable on all drivers.

    Currently it isn’t clear how to determine whether an error or a normal out of data condition has occurred if Fetch() fails.

    Return

      TRUE if a new row is successfully fetched, or FALSE if not.

    Parameters

      - `nOrientation`: One of SQL_FETCH_NEXT, SQL_FETCH_LAST, SQL_FETCH_PRIOR, SQL_FETCH_ABSOLUTE, or SQL_FETCH_RELATIVE (default is SQL_FETCH_NEXT).

      - `nOffset`: the offset (number of records), ignored for some orientations.

  void `ClearColumnData`()

    ClearColumnData.

  int `GetColCount`()

    Fetch the resultset column count.

    Return

      the column count, or zero if there is no resultset.

  const char *`GetColName`(int)

    Fetch a column name.

    Return

      NULL on failure (out of bounds column), or a pointer to an internal copy of the column name.

    Parameters

      - `iCol`: the zero based column index.

  short `GetColType`(int)

    Fetch a column data type.

    The return type code is a an ODBC SQL_ code, one of SQL_UNKNOWN_TYPE, SQL_CHAR, SQL_NUMERIC, SQL_DECIMAL, SQL_INTEGER, SQL_SMALLINT, SQL_FLOAT, SQL_REAL, SQL_DOUBLE, SQL_DATETIME, SQL_VARCHAR, SQL_TYPE_DATE, SQL_TYPE_TIME, SQL_TYPE_TIMESTAMPT.

    Return

      type code or -1 if the column is illegal.

    Parameters

      - `iCol`: the zero based column index.

  const char *`GetColTypeName`(int)

    Fetch a column data type name.

    Returns data source-dependent data type name; for example, “CHAR”, “VARCHAR”, “MONEY”, “LONG VARBINAR”, or “CHAR ( ) FOR BIT DATA”.

    Return

      NULL on failure (out of bounds column), or a pointer to an internal copy of the column dat type name.

    Parameters

      - `iCol`: the zero based column index.

  short `GetColSize`(int)

    Fetch the column width.

    Return

      column width, zero for unknown width columns.

    Parameters

      - `iCol`: the zero based column index.

  short `GetColPrecision`(int)

    Fetch the column precision.

    Return

      column precision, may be zero or the same as column size for columns to which it does not apply.

    Parameters

      - `iCol`: the zero based column index.

  short `GetColNullable`(int)

    Fetch the column nullability.

    Return

      TRUE if the column may contains or FALSE otherwise.

    Parameters

      - `iCol`: the zero based column index.

  const char *`GetColColumnDef`(int)

    Fetch a column default value.

    Returns the default value of a column.

    Return

      NULL if the default value is not dpecified or the internal copy of the default value.

    Parameters

      - `iCol`: the zero based column index.

  int `GetColId`(const char*)

    Fetch column index.

    Gets the column index corresponding with the passed name. The name comparisons are case insensitive.

    Return

      the column index, or -1 if not found.

    Parameters

      - `pszColName`: the name to search for.

  const char *`GetColData`(int, const char* = nullptr)

    Fetch column data.

    Fetches the data contents of the requested column for the currently loaded row. The result is returned as a string regardless of the column type. NULL is returned if an illegal column is given, or if the actual column is “NULL”.

    Return

      pointer to internal column data or NULL on failure.

    Parameters

      - `iCol`: the zero based column to fetch.

      - `pszDefault`: the value to return if the column does not exist, or is NULL. Defaults to NULL.

  const char *`GetColData`(const char*, const char* = nullptr)

    Fetch column data.

    Fetches the data contents of the requested column for the currently loaded row. The result is returned as a string regardless of the column type. NULL is returned if an illegal column is given, or if the actual column is “NULL”.

    Return

      pointer to internal column data or NULL on failure.

    Parameters

      - `pszColName`: the name of the column requested.

      - `pszDefault`: the value to return if the column does not exist, or is NULL. Defaults to NULL.

  int `GetColDataLength`(int)

    GetColDataLength.

  int `GetRowCountAffected`()

    GetRowCountAffected.

  int `GetColumns`(const char *pszTable, const char *pszCatalog = nullptr, const char *pszSchema = nullptr)

    Fetch column definitions for a table.

    The SQLColumn() method is used to fetch the definitions for the columns of a table (or other queryable object such as a view). The column definitions are digested and used to populate the CPLODBCStatement column definitions essentially as if a “SELECT * FROM tablename” had been done; however, no resultset will be available.

    Return

      TRUE on success or FALSE on failure.

    Parameters

      - `pszTable`: the name of the table to query information on. This should not be empty.

      - `pszCatalog`: the catalog to find the table in, use NULL (the default) if no catalog is available.

      - `pszSchema`: the schema to find the table in, use NULL (the default) if no schema is available.

  int `GetPrimaryKeys`(const char *pszTable, const char *pszCatalog = nullptr, const char *pszSchema = nullptr)

    Fetch primary keys for a table.

    The SQLPrimaryKeys() function is used to fetch a list of fields forming the primary key. The result is returned as a result set matching the SQLPrimaryKeys() function result set. The 4th column in the result set is the column name of the key, and if the result set contains only one record then that single field will be the complete primary key.

    Return

      TRUE on success or FALSE on failure.

    Parameters

      - `pszTable`: the name of the table to query information on. This should not be empty.

      - `pszCatalog`: the catalog to find the table in, use NULL (the default) if no catalog is available.

      - `pszSchema`: the schema to find the table in, use NULL (the default) if no schema is available.

  int `GetTables`(const char *pszCatalog = nullptr, const char *pszSchema = nullptr)

    Fetch tables in database.

    The SQLTables() function is used to fetch a list tables in the database. The result is returned as a result set matching the SQLTables() function result set. The 3rd column in the result set is the table name. Only tables of type “TABLE” are returned.

    Return

      TRUE on success or FALSE on failure.

    Parameters

      - `pszCatalog`: the catalog to find the table in, use NULL (the default) if no catalog is available.

      - `pszSchema`: the schema to find the table in, use NULL (the default) if no schema is available.

  void `DumpResult`(FILE *fp, int bShowSchema = FALSE)

    Dump resultset to file.

    The contents of the current resultset are dumped in a simply formatted form to the provided file. If requested, the schema definition will be written first.

    Parameters

      - `fp`: the file to write to. stdout or stderr are acceptable.

      - `bShowSchema`: TRUE to force writing schema information for the rowset before the rowset data itself. Default is FALSE.

  int `CollectResultsInfo`()

    CollectResultsInfo.

  Public Static Functions

  static CPLString `GetTypeName`(int)

    Get name for SQL column type.

    Returns a string name for the indicated type code (as returned from CPLODBCStatement::GetColType()).

    Return

      internal string, “UNKNOWN” if code not recognised.

    Parameters

      - `nTypeCode`: the SQL_ code, such as SQL_CHAR.

  static SQLSMALLINT `GetTypeMapping`(SQLSMALLINT)

    Get appropriate C data type for SQL column type.

    Returns a C data type code, corresponding to the indicated SQL data type code (as returned from CPLODBCStatement::GetColType()).

    Return

      data type code. The valid code is always returned. If SQL code is not recognised, SQL_C_BINARY will be returned.

    Parameters

      - `nTypeCode`: the SQL_ code, such as SQL_CHAR.

  Private Functions

  int `Failed`(int)

    Failed.

  Private Members

  CPLODBCSession *`m_poSession` = nullptr
  HSTMT `m_hStmt` = nullptr
  SQLSMALLINT `m_nColCount` = 0
  char **`m_papszColNames` = nullptr
  SQLSMALLINT *`m_panColType` = nullptr
  char **`m_papszColTypeNames` = nullptr
  CPL_SQLULEN *`m_panColSize` = nullptr
  SQLSMALLINT *`m_panColPrecision` = nullptr
  SQLSMALLINT *`m_panColNullable` = nullptr
  char **`m_papszColColumnDef` = nullptr
  char **`m_papszColValues` = nullptr
  CPL_SQLLEN *`m_panColValueLengths` = nullptr
  char *`m_pszStatement` = nullptr
  size_t `m_nStatementMax` = 0
  size_t `m_nStatementLen` = 0

## cpl_vsi_virtual.h

Functions

VSIVirtualHandle *`VSICreateBufferedReaderHandle`(VSIVirtualHandle *poBaseHandle)

VSIVirtualHandle *`VSICreateBufferedReaderHandle`(VSIVirtualHandle *poBaseHandle, const GByte *pabyBeginningContent, vsi_l_offset nCheatFileSize)

VSIVirtualHandle *`VSICreateCachedFile`(VSIVirtualHandle *poBaseHandle, size_t nChunkSize = 32768, size_t nCacheSize = 0)

VSIVirtualHandle *`VSICreateGZipWritable`(VSIVirtualHandle *poBaseHandle, int nDeflateType, int bAutoCloseBaseHandle)

VSIVirtualHandle *`VSICreateUploadOnCloseFile`(VSIVirtualHandle *poBaseHandle)

Variables

const int `CPL_DEFLATE_TYPE_GZIP` = 0

const int `CPL_DEFLATE_TYPE_ZLIB` = 1

const int `CPL_DEFLATE_TYPE_RAW_DEFLATE` = 2

class `VSIVirtualHandle`
  #include <cpl_vsi_virtual.h>

  Virtual file handle.

  Subclassed by VSISparseFileHandle, VSISubFileHandle, VSIUploadOnCloseHandle

  Public Functions

  virtual int `Seek`(vsi_l_offset nOffset, int nWhence) = 0

    Seek to requested offset.

    Seek to the desired offset (nOffset) in the indicated file.

    This method goes through the VSIFileHandler virtualization and may work on unusual filesystems such as in memory.

    Analog of the POSIX fseek() call.

    Caution: vsi_l_offset is a unsigned type, so SEEK_CUR can only be used for positive seek. If negative seek is needed, use handle->Seek( handle->Tell() + negative_offset, SEEK_SET ).

    Return

      0 on success or -1 one failure.

    Parameters

      - `nOffset`: offset in bytes.

      - `nWhence`: one of SEEK_SET, SEEK_CUR or SEEK_END.

  virtual vsi_l_offset `Tell`() = 0

    Tell current file offset.

    Returns the current file read/write offset in bytes from the beginning of the file.

    This method goes through the VSIFileHandler virtualization and may work on unusual filesystems such as in memory.

    Analog of the POSIX ftell() call.

    Return

      file offset in bytes.

  virtual size_t `Read`(void *pBuffer, size_t nSize, size_t nCount) = 0

    Read bytes from file.

    Reads nCount objects of nSize bytes from the indicated file at the current offset into the indicated buffer.

    This method goes through the VSIFileHandler virtualization and may work on unusual filesystems such as in memory.

    Analog of the POSIX fread() call.

    Return

      number of objects successfully read.

    Parameters

      - `pBuffer`: the buffer into which the data should be read (at least nCount * nSize bytes in size.

      - `nSize`: size of objects to read in bytes.

      - `nCount`: number of objects to read.

  virtual int `ReadMultiRange`(int nRanges, void **ppData, const vsi_l_offset *panOffsets, const size_t *panSizes)

    Read several ranges of bytes from file.

    Reads nRanges objects of panSizes[i] bytes from the indicated file at the offset panOffsets[i] into the buffer ppData[i].

    Ranges must be sorted in ascending start offset, and must not overlap each other.

    This method goes through the VSIFileHandler virtualization and may work on unusual filesystems such as in memory or /vsicurl/.

    Return

      0 in case of success, -1 otherwise.

    Since

      GDAL 1.9.0

    Parameters

      - `nRanges`: number of ranges to read.

      - `ppData`: array of nRanges buffer into which the data should be read (ppData[i] must be at list panSizes[i] bytes).

      - `panOffsets`: array of nRanges offsets at which the data should be read.

      - `panSizes`: array of nRanges sizes of objects to read (in bytes).

  virtual size_t `Write`(const void *pBuffer, size_t nSize, size_t nCount) = 0

    Write bytes to file.

    Writess nCount objects of nSize bytes to the indicated file at the current offset into the indicated buffer.

    This method goes through the VSIFileHandler virtualization and may work on unusual filesystems such as in memory.

    Analog of the POSIX fwrite() call.

    Return

      number of objects successfully written.

    Parameters

      - `pBuffer`: the buffer from which the data should be written (at least nCount * nSize bytes in size.

      - `nSize`: size of objects to read in bytes.

      - `nCount`: number of objects to read.

  virtual int `Eof`() = 0

    Test for end of file.

    Returns TRUE (non-zero) if an end-of-file condition occurred during the previous read operation. The end-of-file flag is cleared by a successful VSIFSeekL() call.

    This method goes through the VSIFileHandler virtualization and may work on unusual filesystems such as in memory.

    Analog of the POSIX feof() call.

    Return

      TRUE if at EOF else FALSE.

  inline virtual int `Flush`()

    Flush pending writes to disk.

    For files in write or update mode and on filesystem types where it is applicable, all pending output on the file is flushed to the physical disk.

    This method goes through the VSIFileHandler virtualization and may work on unusual filesystems such as in memory.

    Analog of the POSIX fflush() call.

    Return

      0 on success or -1 on error.

  virtual int `Close`() = 0

    Close file.

    This function closes the indicated file.

    This method goes through the VSIFileHandler virtualization and may work on unusual filesystems such as in memory.

    Analog of the POSIX fclose() function.

    Return

      0 on success or -1 on failure.

  virtual int `Truncate`(vsi_l_offset nNewSize)

    Truncate/expand the file to the specified size.

    This method goes through the VSIFileHandler virtualization and may work on unusual filesystems such as in memory.

    Analog of the POSIX ftruncate() call.

    Return

      0 on success

    Since

      GDAL 1.9.0

    Parameters

      - `nNewSize`: new size in bytes.

  inline virtual void *`GetNativeFileDescriptor`()

    Returns the “native” file descriptor for the virtual handle.

    This will only return a non-NULL value for “real” files handled by the operating system (to be opposed to GDAL virtual file systems).

    On POSIX systems, this will be a integer value (“fd”) cast as a void*. On Windows systems, this will be the HANDLE.

    Return

      the native file descriptor, or NULL.

  inline virtual VSIRangeStatus `GetRangeStatus`(vsi_l_offset nOffset, vsi_l_offset nLength)

    Return if a given file range contains data or holes filled with zeroes.

    This uses the filesystem capabilities of querying which regions of a sparse file are allocated or not. This is currently only implemented for Linux (and no other Unix derivatives) and Windows.

    Note: A return of VSI_RANGE_STATUS_DATA doesn’t exclude that the extent is filled with zeroes! It must be interpreted as “may

    contain non-zero data”.

    Return

      extent status: VSI_RANGE_STATUS_UNKNOWN, VSI_RANGE_STATUS_DATA or VSI_RANGE_STATUS_HOLE

    Since

      GDAL 2.2

    Parameters

      - `nOffset`: offset of the start of the extent.

      - `nLength`: extent length.

  inline virtual `~VSIVirtualHandle`()

See also

Common Portability Library C API.