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Diffstat (limited to 'include/rtems/rtl/rtl-obj-cache.h')
-rw-r--r-- | include/rtems/rtl/rtl-obj-cache.h | 132 |
1 files changed, 132 insertions, 0 deletions
diff --git a/include/rtems/rtl/rtl-obj-cache.h b/include/rtems/rtl/rtl-obj-cache.h new file mode 100644 index 0000000000..8eacdd316b --- /dev/null +++ b/include/rtems/rtl/rtl-obj-cache.h @@ -0,0 +1,132 @@ +/* + * COPYRIGHT (c) 2012 Chris Johns <chrisj@rtems.org> + * + * The license and distribution terms for this file may be + * found in the file LICENSE in this distribution or at + * http://www.rtems.org/license/LICENSE. + */ +/** + * @file + * + * @ingroup rtems_rtl + * + * @brief RTEMS Run-Time Linker Object File cache buffers a section of the + * object file in a buffer to localise read performance. + * + * This is a simple object file cache that holds a buffer of data from the + * offset in the file the read is requested from. Writes are not supported. + * + * The cache holds the file descriptor, the offset into the file and the amount + * of valid data in the cache. If the file is ever modified the user of the + * cache to responsible for flushing the cache. For example the cache should be + * flused if the file is closed. + * + * The cache can return by reference or by value. By reference allow access to + * the cache buffer. Do not modify the cache's data. By value will copy the + * requested data into the user supplied buffer. + * + * The read by reference call allows you to probe the file's data. For example + * a string in an object file can be an unknown length. You can request a read + * up to the cache's size by reference. The code will attempt to have this data + * in the buffer. If there is not enough data in the file the length will be + * modifed to reflect this. + * + * You can have more than one cache for a single file all looking at different + * parts of the file. + */ + +#if !defined (_RTEMS_RTL_OBJ_CACHE_H_) +#define _RTEMS_RTL_OBJ_CACHE_H_ + +#include <fcntl.h> +#include <stdbool.h> +#include <stdint.h> +#include <stdlib.h> + +#ifdef __cplusplus +extern "C" { +#endif /* __cplusplus */ + +/** + * The buffer cache. + */ +typedef struct rtems_rtl_obj_cache_s +{ + int fd; /**< The file descriptor of the data in the cache. */ + size_t file_size; /**< The size of the file. */ + off_t offset; /**< The base offset of the buffer. */ + size_t size; /**< The size of the cache. */ + size_t level; /**< The amount of data in the cache. A file can be + * smaller than the cache file. */ + uint8_t* buffer; /**< The buffer */ +} rtems_rtl_obj_cache_t; + +/** + * Open a cache allocating a single buffer of the size passed. The default + * state of the cache is flushed. No already open checks are made. + * + * @param cache The cache to initialise. + * @param size The size of the cache. + * @retval true The cache is open. + * @retval false The cache is not open. The RTL error is set. + */ +bool rtems_rtl_obj_cache_open (rtems_rtl_obj_cache_t* cache, size_t size); + +/** + * Close a cache. + * + * @param cache The cache to close. + */ +void rtems_rtl_obj_cache_close (rtems_rtl_obj_cache_t* cache); + +/** + * Flush the cache. Any further read will read the data from the file. + * + * @param cache The cache to flush. + */ +void rtems_rtl_obj_cache_flush (rtems_rtl_obj_cache_t* cache); + +/** + * Read data by reference. The length contains the amount of data that should + * be available in the cache and referenced by the buffer handle. It must be + * less than or equal to the size of the cache. This call will return the + * amount of data that is available. It can be less than you ask if the offset + * and size is past the end of the file. + * + * @param cache The cache to reference data from. + * @param fd The file descriptor. Must be an open file. + * @param offset The offset in the file to reference the data to. + * @param buffer The location to reference the data from. + * @param length The length of data to reference. Can be modified to a + * lesser value and true is still returned so check it. + * @retval true The data referenced is in the cache. + * @retval false The read failed and the RTL error has been set. + */ +bool rtems_rtl_obj_cache_read (rtems_rtl_obj_cache_t* cache, + int fd, + off_t offset, + void** buffer, + size_t* length); + +/** + * Read data by value. The data is copied to the user supplied buffer. + * + * @param cache The cache to read the data from. + * @param fd The file descriptor. Must be an open file. + * @param offset The offset in the file to read the data from. + * @param buffer The location the data is written into. + * @param length The length of data to read. + * @retval true The data has been read from the cache. + * @retval false The read failed and the RTL error has been set. + */ +bool rtems_rtl_obj_cache_read_byval (rtems_rtl_obj_cache_t* cache, + int fd, + off_t offset, + void* buffer, + size_t length); + +#ifdef __cplusplus +} +#endif /* __cplusplus */ + +#endif |