/*
* UCW Library -- Fast Buffered I/O
*
- * (c) 1997--2008 Martin Mares <mj@ucw.cz>
+ * (c) 1997--2011 Martin Mares <mj@ucw.cz>
* (c) 2004 Robert Spalek <robert@ucw.cz>
*
* This software may be freely distributed and used according to the terms
*
* Generally speaking, a fastbuf consists of a buffer and a set of callbacks.
* All front-end functions operate on the buffer and if the buffer becomes
- * empty or fills up, they ask the corresponding callback to solve the
+ * empty or fills up, they ask the corresponding callback to handle the
* situation. Back-ends then differ just in the definition of the callbacks.
- * The state of the fastbuf is represented by `struct fastbuf`, which
- * is a simple structure describing the state of the buffer and pointers
- * to the callback functions.
- *
- * When we are reading from the fastbuf, the buffer is laid out as follows:
- *
- * +----------------+---------------------------+
- * | read data | free space |
- * +----------------+---------------------------+
- * ^ ^ ^ ^
- * buffer bptr bstop bufend
- *
- * Here `bptr` points to the next character to be read. After the last character is
- * read, `bptr == bstop` and the `refill` callback gets called upon the next read
- * attempt to bring further data. This gives us an easy way how to implement @bungetc().
- *
- * When writing, the situation looks like:
- *
- * +--------+--------------+--------------------+
- * | unused | written data | free space |
- * +--------+--------------+--------------------+
- * ^ ^ ^ ^
- * buffer bstop bptr bufend
- *
- * In this case, the `bptr` points at the position where the next character
- * will be written to. When we want to write, but `bptr == bufend`, we call
- * the `spout` hook to flush the data and get an empty buffer.
- *
- * Several dirty tricks can be played:
- *
- * - The `spout`/`refill` hooks can change not only `bptr` and `bstop`, but also
- * the location and size of the buffer; the fb-mem back-end takes advantage of it.
- * - In some cases, the user of the `bdirect` interface can be allowed to modify
- * the data in the buffer to avoid unnecessary copying. If the back-end
- * allows such modifications, it can set `fastbuf->can_overwrite_buffer` accordingly:
- * * 0 if no modification is allowed,
- * * 1 if the user can modify the buffer on the condition that
- * the modifications will be undone before calling the next
- * fastbuf operation
- * * 2 if the user is allowed to overwrite the data in the buffer
- * if @bdirect_read_commit_modified() is called afterwards.
- * In this case, the back-end must be prepared for trimming
- * of the buffer which is done by the commit function.
*
+ * The state of the fastbuf is represented by a <<struct_fastbuf,`struct fastbuf`>>,
+ * which is a simple structure describing the state of the buffer (the pointers
+ * `buffer`, `bufend`), the front-end cursor (`bptr`), the back-end cursor (`bstop`),
+ * position of the back-end cursor in the file (`pos`), some flags (`flags`)
+ * and pointers to the callback functions.
+ *
+ * The buffer can be in one of the following states:
+ *
+ * 1. Flushed:
+ *
+ * +------------------------------------+---------------------------+
+ * | unused | free space |
+ * +------------------------------------+---------------------------+
+ * ^ ^ ^ ^
+ * buffer <= bstop (BE pos) <= bptr (FE pos) <= bufend
+ *
+ * * This schema describes a fastbuf after its initialization or bflush().
+ * * There is no cached data and we are ready for any read or write operation
+ * (well, only if the back-end supports it).
+ * * The interval `[bptr, bufend]` can be used by front-ends
+ * for writing. If it is empty, the `spout` callback gets called
+ * upon the first write attempt to allocate a new buffer. Otherwise
+ * the fastbuf silently comes to the writing mode.
+ * * When a front-end needs to read something, it calls the `refill` callback.
+ * * The pointers can be either all non-`NULL` or all NULL.
+ * * `bstop == bptr` in most back-ends, but it is not necessary. Some
+ * in-memory streams take advantage of this.
+ *
+ * 2. Reading:
+ *
+ * +------------------------------------+---------------------------+
+ * | read data | unused |
+ * +------------------------------------+---------------------------+
+ * ^ ^ ^ ^
+ * buffer <= bptr (FE pos) <= bstop (BE pos) <= bufend
+ *
+ * * If we try to read something, we get to the reading mode.
+ * * No writing is allowed until a flush operation. But note that @bflush()
+ * will simply set `bptr` to `bstop` before `spout`
+ * and it breaks the position of the front-end's cursor,
+ * so the user should seek afwards.
+ * * The interval `[buffer, bstop]` contains a block of data read by the back-end.
+ * `bptr` is the front-end's cursor which points to the next character to be read.
+ * After the last character is read, `bptr == bstop` and the `refill` callback
+ * gets called upon the next read attempt to bring further data.
+ * This gives us an easy way how to implement @bungetc().
+ *
+ * 3. Writing:
+ *
+ * +-----------------------+----------------+-----------------------+
+ * | unused | written data | free space |
+ * +-----------------------+----------------+-----------------------+
+ * ^ ^ ^ ^
+ * buffer <= bstop (BE pos) < bptr (FE pos) <= bufend
+ *
+ * * This schema corresponds to the situation after a write attempt.
+ * * No reading is allowed until a flush operation.
+ * * The `bptr` points at the position where the next character
+ * will be written to. When we want to write, but `bptr == bufend`, we call
+ * the `spout` hook to flush the witten data and get an empty buffer.
+ * * `bstop` usually points at the beginning of the written data,
+ * but it is not necessary.
+ *
+ *
+ * Rules for back-ends:
+ *
+ * - Front-ends are only allowed to change the value of `bptr`, some flags
+ * and if a fatal error occurs, then also `bstop`. Back-ends can rely on it.
+ * - `buffer <= bstop <= bufend` and `buffer <= bptr <= bufend`.
+ * - `pos` should be the real position in the file corresponding to the location of `bstop` in the buffer.
+ * It can be modified by any back-end's callback, but the position of `bptr` (`pos + (bptr - bstop)`)
+ * must stay unchanged after `refill` or `spout`.
+ * - Failed callbacks (except `close`) should use @bthrow().
+ * - Any callback pointer may be NULL in case the callback is not implemented.
+ * - Callbacks can change not only `bptr` and `bstop`, but also the location and size of the buffer;
+ * the fb-mem back-end takes advantage of it.
+ *
+ * - Initialization:
+ * * out: `buffer <= bstop <= bptr <= bufend` (flushed).
+ * * @fb_tie() should be called on the newly created fastbuf.
+ *
+ * - `refill`:
+ * * in: `buffer <= bstop <= bptr <= bufend` (reading or flushed).
+ * * out: `buffer <= bptr <= bstop <= bufend` (reading).
+ * * Resulting `bptr == bstop` signals the end of file.
+ * The next reading attempt will again call `refill` which can succeed this time.
+ * * The callback must also return zero on EOF (iff `bptr == bstop`).
+ *
+ * - `spout`:
+ * * in: `buffer <= bstop <= bptr <= bufend` (writing or flushed).
+ * * out: `buffer <= bstop <= bptr < bufend` (flushed).
+ *
+ * - `seek`:
+ * * in: `buffer <= bstop <= bptr <= bufend` (flushed).
+ * * in: `(ofs >= 0 && whence == SEEK_SET) || (ofs <= 0 && whence == SEEK_END)`.
+ * * out: `buffer <= bstop <= bptr <= bufend` (flushed).
+ *
+ * - `close`:
+ * * in: `buffer <= bstop <= bptr <= bufend` (flushed or after @bthrow()).
+ * * `close` must always free all internal structures, even when it throws an exception.
***/
/**
* for how it works.
**/
struct fastbuf {
- byte is_fastbuf[0]; /* Dummy field for checking of type casts */
byte *bptr, *bstop; /* State of the buffer */
byte *buffer, *bufend; /* Start and end of the buffer */
char *name; /* File name (used for error messages) */
ucw_off_t pos; /* Position of bstop in the file */
+ uns flags; /* See enum fb_flags */
int (*refill)(struct fastbuf *); /* Get a buffer with new data, returns 0 on EOF */
void (*spout)(struct fastbuf *); /* Write buffer data to the file */
int (*seek)(struct fastbuf *, ucw_off_t, int);/* Slow path for @bseek(), buffer already flushed; returns success */
void (*close)(struct fastbuf *); /* Close the stream */
int (*config)(struct fastbuf *, uns, int); /* Configure the stream */
int can_overwrite_buffer; /* Can the buffer be altered? 0=never, 1=temporarily, 2=permanently */
+ struct resource *res; /* The fastbuf can be tied to a resource pool */
};
+/**
+ * Fastbuf flags
+ */
+enum fb_flags {
+ FB_DEAD = 0x1, /* Some fastbuf's method has thrown an exception */
+ FB_DIE_ON_EOF = 0x2, /* Most of read operations throw "fb.eof" on EOF */
+};
+
+/** Tie a fastbuf to a resource in the current resource pool. Returns the pointer to the same fastbuf. **/
+struct fastbuf *fb_tie(struct fastbuf *b); /* Tie fastbuf to a resource if there is an active pool */
+
/***
* === Fastbuf on files [[fbparam]]
*
};
struct cf_section;
-extern struct cf_section fbpar_cf; /** Configuration section with which you can fill the `fb_params` **/
+extern struct cf_section fbpar_cf; /** Configuration section with which you can fill the `fb_params` **/
extern struct fb_params fbpar_def; /** The default `fb_params` **/
/**
* Use @params to select the fastbuf back-end and its parameters or
* pass NULL if you are fine with defaults.
*
- * Dies if the file does not exist.
+ * Raises `ucw.fb.open` if the file does not exist.
**/
struct fastbuf *bopen_file(const char *name, int mode, struct fb_params *params);
struct fastbuf *bopen_file_try(const char *name, int mode, struct fb_params *params); /** Like bopen_file(), but returns NULL on failure. **/
struct fastbuf *bfdopen_internal(int fd, const char *name, uns buflen);
struct fastbuf *bfmmopen_internal(int fd, const char *name, uns mode);
+#ifdef CONFIG_UCW_FB_DIRECT
extern uns fbdir_cheat;
struct asio_queue;
struct fastbuf *fbdir_open_fd_internal(int fd, const char *name, struct asio_queue *io_queue, uns buffer_size, uns read_ahead, uns write_back);
+#endif
void bclose_file_helper(struct fastbuf *f, int fd, int is_temp_file);
* of the buffer temporarily. In this case, set @can_overwrite as described
* in <<internal,Internals>>. If you do not care, keep @can_overwrite zero.
*
- * It is not possible to close this fastbuf.
+ * It is not possible to close this fastbuf. This implies that no tying to
+ * resources takes place.
*/
void fbbuf_init_read(struct fastbuf *f, byte *buffer, uns size, uns can_overwrite);
/**
* Creates a write-only fastbuf which writes into a provided memory buffer.
* The fastbuf structure is allocated by the caller and pointed to by @f.
- * An attempt to write behind the end of the buffer dies.
+ * An attempt to write behind the end of the buffer causes the `ucw.fb.write` exception.
*
* Data are written directly into the buffer, so it is not necessary to call @bflush()
* at any moment.
*
- * It is not possible to close this fastbuf.
+ * It is not possible to close this fastbuf. This implies that no tying to
+ * resources takes place.
*/
void fbbuf_init_write(struct fastbuf *f, byte *buffer, uns size);
* At every moment, you can use `fastbuf->buffer` to gain access to the stream.
***/
+struct mempool;
+
struct fastbuf *fbgrow_create(unsigned basic_size); /** Create the growing buffer pre-allocated to @basic_size bytes. **/
+struct fastbuf *fbgrow_create_mp(struct mempool *mp, unsigned basic_size); /** Create the growing buffer pre-allocated to @basic_size bytes. **/
void fbgrow_reset(struct fastbuf *b); /** Reset stream and prepare for writing. **/
void fbgrow_rewind(struct fastbuf *b); /** Prepare for reading (of already written data). **/
+/**
+ * Can be used in any state of @b (for example when writing or after
+ * @fbgrow_rewind()) to return the pointer to internal buffer and its length in
+ * bytes. The returned buffer can be invalidated by further requests.
+ **/
+uns fbgrow_get_buf(struct fastbuf *b, byte **buf);
+
/***
* === Fastbuf on memory pools [[fbpool]]
*
* buffer, but this time the buffer is allocated from within a memory pool.
***/
-struct mempool;
struct fbpool { /** Structure for fastbufs & mempools. **/
struct fastbuf fb;
struct mempool *mp;
};
/**
- * Initialize a new `fbpool`. The structure is allocated by the caller.
+ * Initialize a new `fbpool`. The structure is allocated by the caller,
+ * so bclose() should not be called and no resource tying takes place.
**/
void fbpool_init(struct fbpool *fb); /** Initialize a new mempool fastbuf. **/
/**
byte *expected_max_bptr;
uns slack_size;
};
-#define FB_ATOMIC(f) ((struct fb_atomic *)(f)->is_fastbuf)
/**
* Open an atomic fastbuf.
fbatomic_internal_write(b);
}
+/***
+ * === Fastbufs atop other fastbufs [[fbmulti]]
+ *
+ * Imagine some code which does massive string processing. It takes an input
+ * buffer, writes a part of it into an output buffer, then some other string
+ * and then the remaining part of the input buffer. Or anything else where you
+ * copy all the data at each stage of the complicated process.
+ *
+ * This backend takes multiple fastbufs and concatenates them formally into
+ * one. You may then read them consecutively as they were one fastbuf at all.
+ *
+ * This backend is read-only.
+ *
+ * This backend is seekable iff all of the supplied fastbufs are seekable.
+ *
+ * You aren't allowed to do anything with the underlying buffers while these
+ * are connected into fbmulti.
+ *
+ * The fbmulti is inited by @fbmulti_create(). It returns an empty fbmulti.
+ * Then you call @fbmulti_append() for each fbmulti.
+ *
+ * If @bclose() is called on fbmulti, all the underlying buffers get closed
+ * recursively.
+ *
+ * If you want to keep an underlying fastbuf open after @bclose, just remove it
+ * by @fbmulti_remove where the second parameter is a pointer to the removed
+ * fastbuf. If you pass NULL, all the underlying fastbufs are removed.
+ *
+ * After @fbmulti_remove, the state of the fbmulti is undefined. The only allowed
+ * operation is either another @fbmulti_remove or @bclose on the fbmulti.
+ ***/
+
+/**
+ * Create an empty fbmulti
+ **/
+struct fastbuf *fbmulti_create(void);
+
+/**
+ * Append a fb to fbmulti
+ **/
+void fbmulti_append(struct fastbuf *f, struct fastbuf *fb);
+
+/**
+ * Remove a fb from fbmulti
+ **/
+void fbmulti_remove(struct fastbuf *f, struct fastbuf *fb);
+
/*** === Configuring stream parameters [[bconfig]] ***/
enum bconfig_type { /** Parameters that could be configured. **/
* Can not be used for fastbufs not returned from function (initialized in a parameter, for example the one from `fbbuf_init_read`).
*/
void bclose(struct fastbuf *f);
+void bthrow(struct fastbuf *f, const char *id, const char *fmt, ...) FORMAT_CHECK(printf,3,4) NONRET; /** Throw exception on a given fastbuf **/
+int brefill(struct fastbuf *f, int allow_eof);
+void bspout(struct fastbuf *f);
void bflush(struct fastbuf *f); /** Write data (if it makes any sense, do not use for in-memory buffers). **/
void bseek(struct fastbuf *f, ucw_off_t pos, int whence); /** Seek in the buffer. See `man fseek` for description of @whence. Only for seekable fastbufs. **/
void bsetpos(struct fastbuf *f, ucw_off_t pos); /** Set position to @pos bytes from beginning. Only for seekable fastbufs. **/
return (f->bptr < f->bstop) ? (int) *f->bptr : bpeekc_slow(f);
}
+int beof_slow(struct fastbuf *f);
+static inline int beof(struct fastbuf *f) /** Have I reached EOF? **/
+{
+ return (f->bptr < f->bstop) ? 0 : beof_slow(f);
+}
+
static inline void bungetc(struct fastbuf *f) /** Return last read character back. Only one back is guaranteed to work. **/
{
f->bptr--;
bputc_slow(f, c);
}
-static inline uns bavailr(struct fastbuf *f)
+static inline uns bavailr(struct fastbuf *f) /** Return the length of the cached data to be read. Do not use directly. **/
{
return f->bstop - f->bptr;
}
-static inline uns bavailw(struct fastbuf *f)
+static inline uns bavailw(struct fastbuf *f) /** Return the length of the buffer available for writing. Do not use directly. **/
{
return f->bufend - f->bptr;
}
/**
* Reads exactly @l bytes of data into @b.
* If at the end of file, it returns 0.
- * If there are data, but less than @l, it dies.
+ * If there are data, but less than @l, it raises `ucw.fb.eof`.
*/
static inline uns breadb(struct fastbuf *f, void *b, uns l)
{
/**
* Reads a line into @b and strips trailing `\n`.
* Returns pointer to the terminating 0 or NULL on `EOF`.
- * Dies if the line is longer than @l.
+ * Raises `ucw.fb.toolong` if the line is longer than @l.
**/
char *bgets(struct fastbuf *f, char *b, uns l);
char *bgets0(struct fastbuf *f, char *b, uns l); /** The same as @bgets(), but for 0-terminated strings. **/
struct bb_t;
/**
* Read a string, strip the trailing `\n` and store it into growing buffer @b.
- * Dies if the line is longer than @limit.
+ * Raises `ucw.fb.toolong` if the line is longer than @limit.
**/
uns bgets_bb(struct fastbuf *f, struct bb_t *b, uns limit);
/**
}
/*** === Direct I/O on buffers ***/
-// TODO Documentation -- what do they do?
-static inline uns
-bdirect_read_prepare(struct fastbuf *f, byte **buf)
+/**
+ * Begin direct reading from fastbuf's internal buffer to avoid unnecessary copying.
+ * The function returns a buffer @buf together with its length in bytes (zero means EOF)
+ * with cached data to be read.
+ *
+ * Some back-ends allow the user to modify the data in the returned buffer to avoid unnecessary.
+ * If the back-end allows such modifications, it can set `f->can_overwrite_buffer` accordingly:
+ *
+ * - 0 if no modification is allowed,
+ * - 1 if the user can modify the buffer on the condition that
+ * the modifications will be undone before calling the next
+ * fastbuf operation
+ * - 2 if the user is allowed to overwrite the data in the buffer
+ * if @bdirect_read_commit_modified() is called afterwards.
+ * In this case, the back-end must be prepared for trimming
+ * of the buffer which is done by the commit function.
+ *
+ * The reading must be ended by @bdirect_read_commit() or @bdirect_read_commit_modified(),
+ * unless the user did not read or modify anything.
+ **/
+static inline uns bdirect_read_prepare(struct fastbuf *f, byte **buf)
{
if (f->bptr == f->bstop && !f->refill(f))
{
return bavailr(f);
}
-static inline void
-bdirect_read_commit(struct fastbuf *f, byte *pos)
+/**
+ * End direct reading started by @bdirect_read_prepare() and move the cursor at @pos.
+ * Data in the returned buffer must be same as after @bdirect_read_prepare() and
+ * @pos must point somewhere inside the buffer.
+ **/
+static inline void bdirect_read_commit(struct fastbuf *f, byte *pos)
{
f->bptr = pos;
}
-static inline void
-bdirect_read_commit_modified(struct fastbuf *f, byte *pos)
+/**
+ * Similar to @bdirect_read_commit(), but accepts also modified data before @pos.
+ * Note that such modifications are supported only if `f->can_overwrite_buffer == 2`.
+ **/
+static inline void bdirect_read_commit_modified(struct fastbuf *f, byte *pos)
{
f->bptr = pos;
f->buffer = pos; /* Avoid seeking backwards in the buffer */
}
-static inline uns
-bdirect_write_prepare(struct fastbuf *f, byte **buf)
+/**
+ * Start direct writing to fastbuf's internal buffer to avoid copy overhead.
+ * The function returns the length of the buffer in @buf (at least one byte)
+ * where we can write to. The operation must be ended by @bdirect_write_commit(),
+ * unless nothing is written.
+ **/
+static inline uns bdirect_write_prepare(struct fastbuf *f, byte **buf)
{
if (f->bptr == f->bufend)
f->spout(f);
return bavailw(f);
}
-static inline void
-bdirect_write_commit(struct fastbuf *f, byte *pos)
+/**
+ * Commit the data written to the buffer returned by @bdirect_write_prepare().
+ * The length is specified by @pos which must point just after the written data.
+ * Also moves the cursor to @pos.
+ **/
+static inline void bdirect_write_commit(struct fastbuf *f, byte *pos)
{
f->bptr = pos;
}