ppsspp/libretro/libretro-common/include/streams/file_stream.h

/* Copyright  (C) 2010-2020 The RetroArch team
 *
 * ---------------------------------------------------------------------------------------
 * The following license statement only applies to this file (file_stream.h).
 * ---------------------------------------------------------------------------------------
 *
 * Permission is hereby granted, free of charge,
 * to any person obtaining a copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

#ifndef __LIBRETRO_SDK_FILE_STREAM_H
#define __LIBRETRO_SDK_FILE_STREAM_H

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <stddef.h>

#include <sys/types.h>

#include <libretro.h>
#include <retro_common_api.h>
#include <retro_inline.h>
#include <boolean.h>

#include <stdarg.h>
#include <vfs/vfs_implementation.h>

/** @defgroup file_stream File Streams
 *
 * All functions in this header will use the VFS interface set in \ref filestream_vfs_init if possible,
 * or else they will fall back to built-in equivalents.
 *
 * @note These functions are modeled after those in the C standard library
 * (and may even use them internally),
 * but identical behavior is not guaranteed.
 *
 * @{
 */

/**
 * The minimum version of the VFS interface required by the \c filestream functions.
 */
#define FILESTREAM_REQUIRED_VFS_VERSION 2
#define FILESTREAM_COPY_REQUIRED_VFS_VERSION 5

RETRO_BEGIN_DECLS

/**
 * Opaque handle to a file stream.
 * @warning This is not interchangeable with \c FILE* or \c retro_vfs_file_handle.
 */
typedef struct RFILE RFILE;

/**
 * Initializes the \c filestream functions to use the VFS interface provided by the frontend.
 * Optional; if not called, all \c filestream functions
 * will use libretro-common's built-in implementations.
 *
 * @param vfs_info The VFS interface returned by the frontend.
 * If \c vfs_info::iface (but \em not \c vfs_info itself) is \c NULL,
 * then libretro-common's built-in VFS implementation will be used.
 */
void filestream_vfs_init(const struct retro_vfs_interface_info* vfs_info);

/**
 * Returns the size of the given file, in bytes.
 *
 * @param stream The open file to query.
 * @return The size of \c stream in bytes,
 * or -1 if there was an error.
 * @see retro_vfs_size_t
 */
int64_t filestream_get_size(RFILE *stream);

/**
 * Sets the size of the given file,
 * truncating or extending it as necessary.
 *
 * @param stream The file to resize.
 * @param length The new size of \c stream, in bytes.
 * @return 0 if the resize was successful,
 * or -1 if there was an error.
 * @see retro_vfs_truncate_t
 */
int64_t filestream_truncate(RFILE *stream, int64_t length);

/**
 * Opens a file for reading or writing.
 *
 * @param path Path to the file to open.
 * Should be in the format described in \ref GET_VFS_INTERFACE.
 * @param mode The mode to open the file in.
 * Should be one or more of the flags in \refitem RETRO_VFS_FILE_ACCESS OR'd together,
 * and \c RETRO_VFS_FILE_ACCESS_READ or \c RETRO_VFS_FILE_ACCESS_WRITE
 * (or both) must be included.
 * @param hints Optional hints to pass to the frontend.
 *
 * @return The opened file, or \c NULL if there was an error.
 * Must be cleaned up with \c filestream_close when no longer needed.
 * @see retro_vfs_open_t
 */
RFILE* filestream_open(const char *path, unsigned mode, unsigned hints);

/**
 * Sets the current position of the file stream.
 * Use this to read specific sections of a file.
 *
 * @param stream The file to set the stream position of.
 * @param offset The new stream position, in bytes.
 * @param seek_position The position to seek from.
 * Should be one of the values in \refitem RETRO_VFS_SEEK_POSITION.
 * @return 0 if the stream position was set successfully,
 * or -1 if there was an error.
 * @see RETRO_VFS_SEEK_POSITION
 * @see retro_vfs_seek_t
 */
int64_t filestream_seek(RFILE *stream, int64_t offset, int seek_position);

/**
 * Reads data from the given file into a buffer.
 * If the read is successful,
 * the file's stream position will advance by the number of bytes read.
 *
 * @param stream The file to read from.
 * @param data The buffer in which to store the read data.
 * @param len The size of \c data, in bytes.
 * @return The number of bytes read,
 * or -1 if there was an error.
 * May be less than \c len, but never more.
 * @see retro_vfs_read_t
 */
int64_t filestream_read(RFILE *stream, void *data, int64_t len);

/**
 * Writes data from a buffer to the given file.
 * If the write is successful,
 * the file's stream position will advance by the number of bytes written.
 *
 * @param stream The file to write to.
 * @param data The buffer containing the data to write.
 * @param len The size of \c data, in bytes.
 * @return The number of bytes written,
 * or -1 if there was an error.
 * May be less than \c len, but never more.
 * @see retro_vfs_write_t
 */
int64_t filestream_write(RFILE *stream, const void *data, int64_t len);

/**
 * Returns the current position of the given file in bytes.
 *
 * @param stream The file to return the stream position for.
 * @return The current stream position in bytes relative to the beginning,
 * or -1 if there was an error.
 * @see retro_vfs_tell_t
 */
int64_t filestream_tell(RFILE *stream);

/**
 * Rewinds the given file to the beginning.
 * Equivalent to <tt>filestream_seek(stream, 0, RETRO_VFS_SEEK_POSITION_START)</tt>.

 * @param stream The file to rewind.
 * May be \c NULL, in which case this function does nothing.
 */
void filestream_rewind(RFILE *stream);

/**
 * Closes the given file.
 *
 * @param stream The file to close.
 * This should have been created with \c filestream_open.
 * Behavior is undefined if \c NULL.
 * @return 0 if the file was closed successfully,
 * or -1 if there was an error.
 * @post \c stream is no longer valid and should not be used,
 * even if this function fails.
 * @see retro_vfs_close_t
 */
int filestream_close(RFILE *stream);

/**
 * Opens a file, reads its contents into a newly-allocated buffer,
 * then closes it.
 *
 * @param path[in] Path to the file to read.
 * Should be in the format described in \ref GET_VFS_INTERFACE.
 * @param buf[out] A pointer to the address of the newly-allocated buffer.
 * The buffer will contain the entirety of the file at \c path.
 * Will be allocated with \c malloc and must be freed with \c free.
 * @param len[out] Pointer to the size of the buffer in bytes.
 * May be \c NULL, in which case the length is not written.
 * Value is unspecified if this function fails.
 * @return 1 if the file was read successfully,
 * 0 if there was an error.
 * @see filestream_write_file
 */
int64_t filestream_read_file(const char *path, void **buf, int64_t *len);

/**
 * Reads a line of text from the given file,
 * up to a given length.
 *
 * Will read to the next newline or until the buffer is full,
 * whichever comes first.
 *
 * @param stream The file to read from.
 * @param s The buffer to write the retrieved line to.
 * Will contain at most \c len - 1 characters
 * plus a null terminator.
 * The newline character (if any) will not be included.
 * The line delimiter must be Unix-style (\c '\n').
 * Carriage returns (\c '\r') will not be treated specially.
 * @param len The length of the buffer \c s, in bytes.
 * @return \s if successful, \c NULL if there was an error.
 */
char* filestream_gets(RFILE *stream, char *s, size_t len);

/**
 * Reads a single character from the given file.
 *
 * @param stream The file to read from.
 * @return The character read, or -1 upon reaching the end of the file.
 */
int filestream_getc(RFILE *stream);

/**
 * Reads formatted text from the given file,
 * with arguments provided as a standard \c va_list.
 *
 * @param stream The file to read from.
 * @param format The string to write, possibly including scanf-compatible format specifiers.
 * @param args Argument list with zero or more elements
 * whose values will be updated according to the semantics of \c format.
 * @return The number of arguments in \c args that were successfully assigned,
 * or -1 if there was an error.
 * @see https://en.cppreference.com/w/c/io/fscanf
 * @see https://en.cppreference.com/w/c/variadic
 */
int filestream_vscanf(RFILE *stream, const char* format, va_list *args);

/**
 * Reads formatted text from the given file.
 *
 * @param stream The file to read from.
 * @param format The string to write, possibly including scanf-compatible format specifiers.
 * @param ... Zero or more arguments that will be updated according to the semantics of \c format.
 * @return The number of arguments in \c ... that were successfully assigned,
 * or -1 if there was an error.
 * @see https://en.cppreference.com/w/c/io/fscanf
 */
int filestream_scanf(RFILE *stream, const char* format, ...);

/**
 * Determines if there's any more data left to read from this file.
 *
 * @param stream The file to check the position of.
 * @return -1 if this stream has reached the end of the file,
 * 0 if not.
 */
int filestream_eof(RFILE *stream);

/**
 * Writes the entirety of a given buffer to a file at a given path.
 * Any file that already exists will be overwritten.
 *
 * @param path Path to the file that will be written to.
 * @param data The buffer to write to \c path.
 * @param size The size of \c data, in bytes.
 * @return \c true if the file was written successfully,
 * \c false if there was an error.
 */
bool filestream_write_file(const char *path, const void *data, int64_t size);

/**
 * Writes the entirety of a given buffer to a file at a given path,
 * by way of a sibling temporary file that is renamed over the target
 * once it is complete. A process that dies partway through leaves
 * either the previous contents of \c path or the new ones, never a
 * partial file.
 *
 * Use this for anything a later run reads back and trusts without a
 * length or checksum of its own, where a truncated file is worse than
 * an absent one.
 *
 * Under a frontend VFS whose rename refuses an existing destination,
 * the target is removed first and the rename retried, so there the
 * replacement is not atomic.
 *
 * @param path Path to the file that will be written to.
 * @param data The buffer to write to \c path.
 * @param size The size of \c data, in bytes.
 * @return \c true if the file was written successfully,
 * \c false if there was an error, in which case \c path is left as it
 * was and no temporary file remains.
 */
bool filestream_write_file_atomic(const char *path, const void *data, int64_t size);

/**
 * Opens the sibling temporary file an atomic write of \c path goes
 * through (\c path with ".tmp" appended), for a writer that produces
 * the contents a piece at a time.  Finish with
 * filestream_commit_atomic(), which closes it either way.
 *
 * @param path Path of the file that will be replaced.
 * @return The temporary file, open for writing, or \c NULL on error.
 */
RFILE *filestream_open_atomic(const char *path);

/**
 * Closes a file from filestream_open_atomic() and, if \c ok and the
 * close succeeded, renames it over \c path, exactly as
 * filestream_write_file_atomic() does.
 *
 * @param file The file returned by filestream_open_atomic(); always
 * closed and freed.
 * @param path The same path it was opened for.
 * @param ok Whether the caller wrote everything it meant to.
 * @return 0 if \c path now holds the new contents; -1 if the write or
 * close failed, in which case the temporary file is deleted and \c path
 * is left as it was; 1 if the contents are complete in the temporary
 * file but could not be renamed into place, in which case the temporary
 * file is left for the caller to copy or delete.
 */
int filestream_commit_atomic(RFILE *file, const char *path, bool ok);

/**
 * Writes a single character to the given file.
 *
 * @param stream The file to write to.
 * @param c The character to write.
 * @return The character written,
 * or -1 if there was an error.
 * Will return -1 if \c stream is \c NULL.
 */
int filestream_putc(RFILE *stream, int c);

/**
 * Writes formatted text to the given file,
 * with arguments provided as a standard \c va_list.
 *
 * @param stream The file to write to.
 * @param format The string to write, possibly including printf-compatible format specifiers.
 * @param args A list of arguments to be formatted and inserted in the resulting string.
 * @return The number of characters written,
 * or -1 if there was an error.
 * @see https://en.cppreference.com/w/c/io/vfprintf
 * @see https://en.cppreference.com/w/c/variadic
 */
int filestream_vprintf(RFILE *stream, const char* format, va_list args);

/**
 * Writes formatted text to the given file.
 *
 * @param stream The file to write to.
 * @param format The string to write, possibly including printf-compatible format specifiers.
 * @param ... Zero or more arguments to be formatted and inserted into the resulting string.
 * @return The number of characters written,
 * or -1 if there was an error.
 * @see https://en.cppreference.com/w/c/io/printf
 */
int filestream_printf(RFILE *stream, const char* format, ...);

/**
 * Checks if there was an error in using the given file stream.
 *
 * @param stream The file stream to check for errors.
 * @return \c true if there was an error in using this stream,
 * \c false if not or if \c stream is \c NULL.
 */
int filestream_error(RFILE *stream);

/**
 * Flushes pending writes to the operating system's file layer.
 * There is no guarantee that pending writes will be written to disk immediately.
 *
 * @param stream The file to flush.
 * @return 0 if the flush was successful,
 * or -1 if there was an error.
 * @see retro_vfs_flush_t
 */
int filestream_flush(RFILE *stream);

/**
 * Deletes the file at the given path.
 * If the file is open by any process,
 * the behavior is platform-specific.
 *
 * @note This function might or might not delete directories recursively,
 * depending on the platform and the underlying VFS implementation.
 *
 * @param path The file to delete.
 * @return 0 if the file was deleted successfully,
 * or -1 if there was an error.
 * @see retro_vfs_remove_t
 */
int filestream_delete(const char *path);

/**
 * Moves a file to a new location, with a new name.
 *
 * @param old_path Path to the file to rename.
 * @param new_path The target name and location of the file.
 * @return 0 if the file was renamed successfully,
 * or -1 if there was an error.
 * @see retro_vfs_rename_t
 */
int filestream_rename(const char *old_path, const char *new_path);

/**
 * Copies a regular file to a new location, replacing an existing one,
 * and does not return until it is done.
 *
 * Kept for callers that predate VFS API v5. It copies through
 * \c filestream_open/read/write and does not use the platform's copy
 * primitive; new code should use \c filestream_copy_begin, which does
 * and does not block.
 *
 * @param src_path Path to the file to copy.
 * @param dst_path The target name and location of the file.
 * @return 0 if the file was copied successfully,
 * or -1 if there was an error (no partial \c dst_path is left behind).
 * @see filestream_copy_begin
 */
int filestream_copy(const char *src_path, const char *dst_path);

/**
 * Starts copying a regular file without moving any of it yet.
 * Wraps \c retro_vfs_copy_begin_t; see it for the full contract. The
 * caller advances the copy with \c filestream_copy_step; no thread is
 * involved unless the caller supplies one.
 *
 * @param src_path Path to the file to copy. Must be a regular file.
 * @param dst_path Full path of the destination. Must differ from \c src_path.
 * @param flags Bitwise combination of \c RETRO_VFS_COPY flags, or 0.
 * @return A handle for \c filestream_copy_step and \c filestream_copy_close,
 * or \c NULL if the copy could not start (including when the frontend
 * does not offer VFS API v5).
 */
struct retro_vfs_copy_handle *filestream_copy_begin(const char *src_path, const char *dst_path, unsigned flags);

/**
 * Advances a copy started with \c filestream_copy_begin by at most
 * \c max_bytes and reports its state. See \c retro_vfs_copy_step_t for
 * how to use the budget as a latency/throughput dial.
 *
 * @param max_bytes Upper bound on bytes moved by this call; 0 selects a
 * default sized for a frame loop.
 * @return One of the \c RETRO_VFS_COPY_STATUS values.
 */
int filestream_copy_step(struct retro_vfs_copy_handle *handle, int64_t max_bytes, int64_t *bytes_done, int64_t *bytes_total);

/**
 * Releases a copy handle, cancelling the copy if it is still running.
 * See \c retro_vfs_copy_close_t.
 *
 * @return 0 if the copy had completed successfully, otherwise -1.
 */
int filestream_copy_close(struct retro_vfs_copy_handle *handle);

/**
 * Compares and verifies files.
 *
 * @param src_path Path to the file.
 * @param dst_path Path to the other file.
 * @return 0 if the files are equal,
 * or -1 if there was an error.
 */
int filestream_cmp(const char *src_path, const char *dst_path);

/**
 * Get the path that was used to open a file.
 *
 * @param stream The file to get the path of.
 * @return The path that was used to open \c stream,
 * or \c NULL if there was an error.
 * The string is owned by \c stream and must not be modified or freed by the caller.
 */
const char* filestream_get_path(RFILE *stream);

/**
 * Borrowed read-only pointer to the entire file, when \c stream is
 * backed by a memory map.
 *
 * Open with \c RETRO_VFS_FILE_ACCESS_HINT_FREQUENT_ACCESS to ask for
 * a mapping.  The hint has always produced one, but the map was
 * reachable only from inside the read path, which copies out of it -
 * so consumers of the hint paid for a copy of data that was already
 * addressable.  Use this when the file is to be read rather than
 * owned: compared against a buffer, hashed, or handed to a parser
 * that takes a base pointer.
 *
 * \c NULL is a normal answer rather than an error - the platform may
 * have no mapping support, the hint may not have been given, or the
 * stream may come from a frontend-supplied VFS - so a caller must
 * keep its ordinary read path and treat this purely as a fast lane.
 *
 * @param stream The file to get the mapping of.
 * @param len Filled with the mapped length, or 0 when there is no
 * mapping.  May be \c NULL.
 * @return Pointer to the mapped file, or \c NULL if it is not mapped.
 * The mapping is owned by \c stream, is valid only until \c stream is
 * closed, and must not be written or freed by the caller.
 */
const uint8_t *filestream_get_mapped_ptr(RFILE *stream, int64_t *len);

typedef const uint8_t *(*filestream_mapped_ptr_cb_t)(void *hfile, int64_t *len);
void filestream_set_mapped_ptr_cb(filestream_mapped_ptr_cb_t cb);

/**
 * Ask the OS to start reading [offset, offset + len) of \c stream into
 * memory ahead of a read or a touch of its mapping. A hint: it returns
 * at once and does nothing on a frontend-supplied VFS or where the
 * platform has no such request. See retro_vfs_file_prefetch_impl().
 */
void filestream_prefetch(RFILE *stream, uint64_t offset, uint64_t len);

/**
 * Size of the window filestream_vscanf() reads and scans at a time,
 * i.e. the furthest a single conversion can reach.
 *
 * Named so a test can drive input either side of it rather than
 * assume a value, the way the compare window below is.
 */
#define FILESTREAM_SCANF_WINDOW 4096

/**
 * Size of the buffer filestream_matches_buf() compares through when
 * the file is not mapped.
 *
 * Exposed so a test can aim at the real boundary rather than a
 * remembered one - a boundary case pointed at the wrong offset is
 * just another mid-file check under a boundary's name.
 *
 * The ceiling is a stack budget, not a throughput one: this buffer is
 * a local, and the smallest thread stack in the tree is GEKKO's
 * 8 KiB (the GEKKO STACKSIZE in rthreads.c), with 32 KiB on 3DS and
 * 64 KiB on Vita. Larger reads are faster - at or above the VFS's
 * own 64 KiB stdio buffer they bypass it entirely - but the platforms
 * that take this path are the ones without memory mapping, which are
 * the same ones with those stacks.
 */
#define FILESTREAM_MATCHES_BUF_WINDOW 1024

/**
 * Does the file at \c path hold exactly \c len bytes equal to
 * \c data?
 *
 * For the common "has this changed since I last wrote it?" question,
 * where the answer decides whether to write at all.  Callers used to
 * answer it by reading the whole file into a fresh allocation,
 * comparing, and freeing - paying a full-size malloc and a full-file
 * read even when a size mismatch made the answer free.
 *
 * This allocates nothing: it settles a size mismatch without reading,
 * compares in place against the memory map where the platform offers
 * one, falls back to a fixed window otherwise, and stops at the first
 * differing byte.
 *
 * @param path The file to compare against.
 * @param data The buffer to compare with. May be \c NULL only when
 * \c len is 0.
 * @param len The number of bytes in \c data.
 * @return \c true only if the file exists, is exactly \c len bytes,
 * and every byte matches. A missing or unreadable file is \c false,
 * not an error - the caller's next step is the same either way.
 */
bool filestream_matches_buf(const char *path, const void *data, size_t len);

/**
 * Determines if a file exists at the given path.
 *
 * @param path The path to check for existence.
 * @return \c true if a file exists at \c path,
 * \c false if not or if \c path is \c NULL or empty.
 */
bool filestream_exists(const char *path);

/**
 * Reads a line from the given file into a newly-allocated buffer.
 *
 * @param stream The file to read from.
 * @return Pointer to the line read from \c stream,
 * or \c NULL if there was an error.
 * Must be freed with \c free when no longer needed.
 */
char* filestream_getline(RFILE *stream);

/**
 * Returns the open file handle
 * that was originally returned by the VFS interface.
 *
 * @param stream File handle returned by \c filestream_open.
 * @return The file handle returned by the underlying VFS implementation.
 */
libretro_vfs_implementation_file* filestream_get_vfs_handle(RFILE *stream);

/**
 * filestream_punch_hole:
 * @stream: file handle.
 * @offset: byte offset to start deallocating at.
 * @len   : number of bytes to deallocate.
 *
 * Deallocate a range within a file, leaving the file's length unchanged
 * and subsequent reads of the range returning zeroes. This is what makes a
 * sparse image sparse: a disk image that is mostly untouched occupies only
 * the blocks that were actually written.
 *
 * Not every backend can do this, and that is the normal case rather than
 * an error. It works when the stream came from libretro-common's own
 * implementation on a filesystem that supports it -- fallocate() with
 * FALLOC_FL_PUNCH_HOLE on Linux, FSCTL_SET_ZERO_DATA on Windows. It does
 * not work when the frontend supplied its own VFS, because a frontend
 * handle need not be a file at all and the interface exposes no
 * descriptor. Rather than extend the frontend ABI for one operation that
 * most backends cannot implement, this is a capability: callers ask, and
 * fall back to writing zeroes when the answer is no.
 *
 * Returns: 0 if the range was deallocated, -1 if the backend cannot do it
 * or the call failed. A caller that must guarantee zeroes still has to
 * write them when this returns -1; the only thing lost is the space
 * saving.
 */
int filestream_punch_hole(RFILE *stream, int64_t offset, int64_t len);

/**
 * filestream_get_sparse_granularity:
 * @stream: file handle.
 *
 * The allocation unit of the filesystem holding this file: the smallest
 * span that filestream_punch_hole can actually deallocate. Punching a
 * range shorter than this, or one not aligned to it, is accepted and
 * frees nothing, so a caller that wants sparse files has to work in
 * multiples of this value rather than assuming 4096.
 *
 * On Windows this is the cluster size on most filesystems, but on NTFS
 * it is the compression unit -- 16 clusters, capped at 64K -- because
 * that is the span NTFS actually deallocates. A 4K-cluster NTFS volume,
 * the common case, frees in 64K chunks, so punching a single cluster
 * frees nothing. On POSIX it is the block size the filesystem reports
 * for the file.
 *
 * Returns: the granularity in bytes, or 0 when it cannot be determined --
 * from a frontend-supplied VFS, for instance, which has no descriptor to
 * ask about. A caller that gets 0 should either skip hole punching or
 * pick a conservative unit; it must not treat 0 as "no alignment
 * needed".
 */
int64_t filestream_get_sparse_granularity(RFILE *stream);

RETRO_END_DECLS

/** @} */

#endif