/* ====================================================================
 * The Apache Software License, Version 1.1
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 * Copyright (c) 2000 The Apache Software Foundation.  All rights
 * reserved.
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 * modification, are permitted provided that the following conditions
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#ifndef AP_BUCKETS_H
#define AP_BUCKETS_H

#include "httpd.h"
#include "apr_general.h"
#include "apr_mmap.h"
#include "apr_errno.h"
#include "ap_ring.h"
#ifdef HAVE_SYS_UIO_H
#include <sys/uio.h>	/* for struct iovec */
#endif
#ifdef HAVE_STDARG_H
#include <stdarg.h>
#endif

/**
 * @package Bucket Brigades
 */

/*
 * The one-sentence buzzword-laden overview: Bucket brigades represent
 * a complex data stream that can be passed through a layered IO
 * system without unnecessary copying. A longer overview follows...
 *
 * A bucket brigade is a doubly linked list of buckets, so we
 * aren't limited to inserting at the front and removing at the end.
 * Buckets are only passed around as members of a brigade, although
 * singleton buckets can occur for short periods of time.
 *
 * Buckets are data stores of varous types. They can refer to data in
 * memory, or part of a file or mmap area, or the output of a process,
 * etc. Buckets also have some type-dependent accessor functions:
 * read, split, setaside, and destroy.
 *
 * read returns the address and size of the data in the bucket. If the
 * data isn't in memory then it is read in and the bucket changes type
 * so that it can refer to the new location of the data. If all the
 * data doesn't fit in the bucket then a new bucket is inserted into
 * the brigade to hold the rest of it.
 *
 * split divides the data in a bucket into two regions. After a split
 * the original bucket refers to the first part of the data and a new
 * bucket inserted into the brigade after the original bucket refers
 * to the second part of the data. Reference counts are maintained as
 * necessary.
 *
 * setaside ensures that the data in the bucket has a long enough
 * lifetime. Sometimes it is convenient to create a bucket referring
 * to data on the stack in the expectation that it will be consumed
 * (output to the network) before the stack is unwound. If that
 * expectation turns out not to be valid, the setaside function is
 * called to move the data somewhere safer.
 *
 * destroy maintains the reference counts on the resources used by a
 * bucket and frees them if necessary.
 *
 * To write a bucket brigade, they are first made into an iovec, so that we
 * don't write too little data at one time.  Currently we ignore compacting the
 * buckets into as few buckets as possible, but if we really want good
 * performance, then we need to compact the buckets before we convert to an
 * iovec, or possibly while we are converting to an iovec.
 */

/* The types of bucket brigades the code knows about.  We don't really need
 * this enum.  All access to the bucket brigades is done through function
 * pointers in the bucket type.  However, when we start to do conversion
 * routines, this enum will be a huge performance benefit, so we leave it
 * alone.
 */
typedef enum {
    AP_BUCKET_HEAP,
    AP_BUCKET_TRANSIENT,
    AP_BUCKET_FILE,
    AP_BUCKET_MMAP,
    AP_BUCKET_IMMORTAL,
    AP_BUCKET_POOL,
    AP_BUCKET_PIPE,
    AP_BUCKET_EOS        /* End-of-stream bucket.  Special case to say this is
                          * the end of the brigade so all data should be sent
                          * immediately.
			  */
} ap_bucket_type_e;

#define AP_END_OF_BRIGADE       -1

/**
 * Forward declaration of the main types.
 */

typedef struct ap_bucket_brigade ap_bucket_brigade;

typedef struct ap_bucket ap_bucket;

/**
 * ap_bucket_t structures are allocated on the malloc() heap and
 * their lifetime is controlled by the parent ap_brigade_t
 * structure. Buckets can move from one brigade to another e.g. by
 * calling ap_brigade_concat(). In general the data in a bucket has
 * the same lifetime as the bucket and is freed when the bucket is
 * destroyed; if the data is shared by more than one bucket (e.g.
 * after a split) the data is freed when the last bucket goes away.
 */
struct ap_bucket {
    /** Links to the rest of the brigade */
    AP_RING_ENTRY(ap_bucket) link;
    /** The type of bucket.  These types can be found in the enumerated
     *  type above */
    ap_bucket_type_e type;
    /** type-dependent data hangs off this pointer */
    void *data;	
    /** The length of the data in the bucket.  This could have been implemented
     *  with a function, but this is an optimization, because the most
     *  common thing to do will be to get the length.  If the length is unknown,
     *  the value of this field will be -1.
     */
    apr_off_t length;

    /** The file offset. Applicable for AP_BUCKET_FILE types only.
     */
    apr_off_t offset;

    /** @tip all of these function pointers may be replaced by some
     *  other means for getting to the functions, like a an index into
     *  a table.  In any case, these functions will always be available.
     */

    /**
     * Free the private data and any resources used by the bucket
     * (if they aren't shared with another bucket).
     * @param data The private data pointer from the bucket to be destroyed
     */
    void (*destroy)(void *data);

    /** Read the data from the bucket.
     * @param b The bucket to read from
     * @param str A place to store the data read.  Allocation should only be
     *            done if absolutely necessary. 
     * @param len The amount of data read,
     *            or -1 (AP_END_OF_BRIGADE) if there is no more data
     * @param block Should this read function block if there is more data that
     *              cannot be read immediately.
     * @deffunc apr_status_t read(ap_bucket *b, const char **str, apr_ssize_t *len, int block)
     */
    apr_status_t (*read)(ap_bucket *b, const char **str, apr_ssize_t *len, int block);
    
    /** Make it possible to set aside the data. For most bucket types this is
     *  a no-op; buckets containing data that dies when the stack is un-wound
     *  must convert the bucket into a heap bucket.
     * @param e The bucket to convert
     * @deffunc apr_status_t setaside(ap_bucket *e)
     */
    apr_status_t (*setaside)(ap_bucket *e);

    /** Split one bucket in two at the specified position
     * @param e The bucket to split
     * @param point The offset of the first byte in the new bucket
     * @deffunc apr_status_t split(ap_bucket *e, apr_off_t point)
     */
    apr_status_t (*split)(ap_bucket *e, apr_off_t point);
};

/** A list of buckets */
struct ap_bucket_brigade {
    /** The pool to associate the brigade with.  The data is not allocated out
     *  of the pool, but a cleanup is registered with this pool.  If the 
     *  brigade is destroyed by some mechanism other than pool destruction,
     *  the destroying function is responsible for killing the cleanup.
     */
    apr_pool_t *p;
    /** The buckets in the brigade are on this list. */
    /*
     * XXX: the ap_bucket_list tag shouldn't me necessary but
     * aparrently without it this fails to compile on Windows.
     */
    AP_RING_HEAD(ap_bucket_list, ap_bucket) list;
};

/**
 * Wrappers around the RING macros to reduce the verbosity of the code
 * that handles bucket brigades.
 */
#define AP_BRIGADE_SENTINEL(b)	AP_RING_SENTINEL(&(b)->list, ap_bucket, link)

#define AP_BRIGADE_EMPTY(b)	AP_RING_EMPTY(&(b)->list, ap_bucket, link)

#define AP_BRIGADE_FIRST(b)	AP_RING_FIRST(&(b)->list)
#define AP_BRIGADE_LAST(b)	AP_RING_LAST(&(b)->list)

#define AP_BRIGADE_FOREACH(e, b)					\
	AP_RING_FOREACH((e), &(b)->list, ap_bucket, link)

#define AP_BRIGADE_INSERT_HEAD(b, e)					\
	AP_RING_INSERT_HEAD(&(b)->list, (e), ap_bucket, link)
#define AP_BRIGADE_INSERT_TAIL(b, e)					\
	AP_RING_INSERT_TAIL(&(b)->list, (e), ap_bucket, link)

#define AP_BRIGADE_CONCAT(a, b)						\
	AP_RING_CONCAT(&(a)->list, &(b)->list, ap_bucket, link)

#define AP_BRIGADE_UNSPLICE(a, b) AP_RING_UNSPLICE((a), (b), link)

#define AP_BUCKET_INSERT_BEFORE(a, b)					\
	AP_RING_INSERT_BEFORE((a), (b), link)
#define AP_BUCKET_INSERT_AFTER(a, b)					\
	AP_RING_INSERT_AFTER((a), (b), link)

#define AP_BUCKET_NEXT(e)	AP_RING_NEXT((e), link)
#define AP_BUCKET_PREV(e)	AP_RING_PREV((e), link)

#define AP_BUCKET_REMOVE(e)	AP_RING_REMOVE((e), link)

/**
 * General-purpose reference counting for the varous bucket types.
 *
 * Any bucket type that keeps track of the resources it uses (i.e.
 * most of them except for IMMORTAL, TRANSIENT, and EOS) needs to
 * attach a reference count to the resource so that it can be freed
 * when the last bucket that uses it goes away. Resource-sharing may
 * occur because of bucket splits or buckets that refer to globally
 * cached data. */

/**
 * The structure used to manage the shared resource must start with an
 * ap_bucket_refcount which is updated by the general-purpose refcount
 * code. A pointer to the bucket-type-dependent private data structure
 * can be cast to a pointer to an ap_bucket_refcount and vice versa.
 */
typedef struct ap_bucket_refcount ap_bucket_refcount;
struct ap_bucket_refcount {
    int          refcount;
};

/**
 * The data pointer of a refcounted bucket points to an
 * ap_bucket_shared structure which describes the region of the shared
 * object that this bucket refers to. The ap_bucket_shared isn't a
 * fully-fledged bucket type: it is a utility type that proper bucket
 * types are based on.
 */
typedef struct ap_bucket_shared ap_bucket_shared;
struct ap_bucket_shared {
    /** start of the data in the bucket relative to the private base pointer */
    apr_off_t start;
    /** end of the data in the bucket relative to the private base pointer */
    apr_off_t end;
    /** pointer to the real private data of the bucket,
     * which starts with an ap_bucket_refcount */
    void *data;
};


/*  *****  Non-reference-counted bucket types  *****  */


typedef struct ap_bucket_simple ap_bucket_simple;

/**
 * TRANSIENT and IMMORTAL buckets don't have much to do with looking
 * after the memory that they refer to so they share a lot of their
 * implementation.
 */
struct ap_bucket_simple {
    /** The start of the data in the bucket */
    const char    *start;
    /** The end of the data in the bucket */
    const char    *end;
};


/*  *****  Reference-counted bucket types  *****  */


typedef struct ap_bucket_heap ap_bucket_heap;

/**
 * A bucket referring to data allocated off the heap.
 */
struct ap_bucket_heap {
    /** Number of buckets using this memory */
    ap_bucket_refcount  refcount;
    /** The start of the data actually allocated.  This should never be
     * modified, it is only used to free the bucket.
     */
    char    *base;
    /** how much memory was allocated.  This may not be necessary */
    size_t  alloc_len;
};

typedef struct ap_bucket_mmap ap_bucket_mmap;

/**
 * A bucket referring to an mmap()ed file
 */
struct ap_bucket_mmap {
    /** Number of buckets using this memory */
    ap_bucket_refcount  refcount;
    /** The mmap this sub_bucket refers to */
    apr_mmap_t *mmap;
};

/*  *****  Bucket Brigade Functions  *****  */

/**
 * Create a new bucket brigade.  The bucket brigade is originally empty.
 * @param The pool to associate with the brigade.  Data is not allocated out
 *        of the pool, but a cleanup is registered.
 * @return The empty bucket brigade
 * @deffunc ap_bucket_brigade *ap_brigade_create(apr_pool_t *p)
 */
API_EXPORT(ap_bucket_brigade *) ap_brigade_create(apr_pool_t *p);

/**
 * destroy an enitre bucket brigade.  This includes destroying all of the
 * buckets within the bucket brigade's bucket list. 
 * @param b The bucket brigade to destroy
 * @deffunc apr_status_t ap_brigade_destroy(ap_bucket_brigade *b)
 */
API_EXPORT(apr_status_t) ap_brigade_destroy(ap_bucket_brigade *b);

/**
 * Split a bucket brigade into two, such that the given bucket is the
 * first in the new bucket brigade. This function is useful when a
 * filter wants to pass only the initial part of a brigade to the next
 * filter.
 * @param b The brigade to split
 * @param e The first element of the new brigade
 * @return The new brigade
 * @deffunc ap_bucket_brigade *ap_brigade_split(ap_bucket_brigade *b, ap_bucket *e)
 */
API_EXPORT(ap_bucket_brigade *) ap_brigade_split(ap_bucket_brigade *b,
						 ap_bucket *e);

/**
 * consume nbytes from beginning of b -- call ap_bucket_destroy as
 * appropriate, and/or modify start on last element 
 * @param b The brigade to consume data from
 * @param nbytes The number of bytes to consume
 * @deffunc void ap_brigade_consume(ap_bucket_brigade *b, int nbytes) */
API_EXPORT(void) ap_brigade_consume(ap_bucket_brigade *b, int nbytes);

/**
 * create an iovec of the elements in a bucket_brigade... return number 
 * of elements used.  This is useful for writing to a file or to the
 * network efficiently.
 * @param The bucket brigade to create the iovec out of
 * @param The iovec to create
 * @param The number of elements in the iovec
 * @return The number of iovec elements actually filled out.
 * @deffunc int ap_brigade_to_iovec(ap_bucket_brigade *b, struct iovec *vec, int nvec);
 */
API_EXPORT(int) ap_brigade_to_iovec(ap_bucket_brigade *b, 
				    struct iovec *vec, int nvec);

/**
 * This function writes a list of strings into a bucket brigade.  We just 
 * allocate a new heap bucket for each string.
 * @param b The bucket brigade to add to
 * @param va A list of strings to add
 * @return The number of bytes added to the brigade
 * @deffunc int ap_brigade_vputstrs(ap_bucket_brigade *b, va_list va)
 */
API_EXPORT(int) ap_brigade_vputstrs(ap_bucket_brigade *b, va_list va);

/**
 * This function writes an unspecified number of strings into a bucket brigade.
 * We just allocate a new heap bucket for each string.
 * @param b The bucket brigade to add to
 * @param ... The strings to add
 * @return The number of bytes added to the brigade
 * @deffunc int ap_brigade_putstrs(ap_bucket_brigade *b, ...)
 */
API_EXPORT_NONSTD(int) ap_brigade_putstrs(ap_bucket_brigade *b, ...);

/**
 * Evaluate a printf and put the resulting string into a bucket at the end 
 * of the bucket brigade.
 * @param b The brigade to write to
 * @param fmt The format of the string to write
 * @param ... The arguments to fill out the format
 * @return The number of bytes added to the brigade
 * @deffunc int ap_brigade_printf(ap_bucket_brigade *b, const char *fmt, ...) 
 */
API_EXPORT_NONSTD(int) ap_brigade_printf(ap_bucket_brigade *b, const char *fmt, ...);

/**
 * Evaluate a printf and put the resulting string into a bucket at the end 
 * of the bucket brigade.
 * @param b The brigade to write to
 * @param fmt The format of the string to write
 * @param va The arguments to fill out the format
 * @return The number of bytes added to the brigade
 * @deffunc int ap_brigade_vprintf(ap_bucket_brigade *b, const char *fmt, va_list va) 
 */
API_EXPORT(int) ap_brigade_vprintf(ap_bucket_brigade *b, const char *fmt, va_list va);


/*  *****  Bucket Functions  *****  */

/**
 * free the resources used by a bucket. If multiple buckets refer to
 * the same resource it is freed when the last one goes away.
 * @param e The bucket to destroy
 * @deffunc apr_status_t ap_bucket_destroy(ap_bucket *e)
 */
API_EXPORT(apr_status_t) ap_bucket_destroy(ap_bucket *e);


/*  *****  Shared reference-counted buckets  *****  */

/**
 * Initialize a bucket containing reference-counted data that may be
 * shared. The caller must allocate the bucket if necessary and
 * initialize its type-dependent fields, and allocate and initialize
 * its own private data structure. This function should only be called
 * by type-specific bucket creation functions.
 * @param b The bucket to initialize,
 *          or NULL if a new one should be allocated
 * @param data A pointer to the private data structure
 *             with the reference count at the start
 * @param start The start of the data in the bucket
 *              relative to the private base pointer
 * @param end The end of the data in the bucket
 *            relative to the private base pointer
 * @return The new bucket, or NULL if allocation failed
 * @deffunc API_EXPORT(ap_bucket *) ap_bucket_shared_create(ap_bucket_refcount *r, apr_off_t start, apr_off_t end) */
API_EXPORT(ap_bucket *) ap_bucket_make_shared(ap_bucket *b, void *data,
					      apr_off_t start, apr_off_t end);

/**
 * Decrement the refcount of the data in the bucket and free the
 * ap_bucket_shared structure. This function should only be called by
 * type-specific bucket destruction functions.
 * @param data The private data pointer from the bucket to be destroyed
 * @return NULL if nothing needs to be done,
 *         otherwise a pointer to the private data structure which
 *         must be destroyed because its reference count is zero
 * @deffunc API_EXPORT(void *) ap_bucket_shared_destroy(ap_bucket *b) */
API_EXPORT(void *) ap_bucket_destroy_shared(void *data);

/**
 * Split a bucket into two at the given point, and adjust the refcount
 * to the underlying data. Most reference-counting bucket types will
 * be able to use this function as their split function without any
 * additional type-specific handling.
 * @param b The bucket to be split
 * @param point The offset of the first byte in the new bucket
 * @return APR_EINVAL if the point is not within the bucket;
 *         APR_ENOMEM if allocation failed;
 *         or APR_SUCCESS
 * @deffunc API_EXPORT(apr_status_t) ap_bucket_shared_split(ap_bucket *b, apr_off_t point)
 */
API_EXPORT_NONSTD(apr_status_t) ap_bucket_split_shared(ap_bucket *b, apr_off_t point);


/*  *****  Functions to Create Buckets of varying type  *****  */

/**
 * Each bucket type foo has two initialization functions:
 * ap_bucket_make_foo which sets up some already-allocated memory as a
 * bucket of type foo; and ap_bucket_create_foo which allocates memory
 * for the bucket, calls ap_bucket_make_foo, and initializes the
 * bucket's list pointers. The ap_bucket_make_foo functions are used
 * inside the bucket code to change the type of buckets in place;
 * other code should call ap_bucket_create_foo. All the initialization
 * functions change nothing if they fail.
 */

/*
 * This macro implements the guts of ap_bucket_create_foo
 */
#define ap_bucket_do_create(do_make)		\
    do {					\
	ap_bucket *b, *ap__b;			\
	b = calloc(1, sizeof(*b));		\
	if (b == NULL) {			\
	    return NULL;			\
	}					\
	ap__b = do_make;			\
	if (ap__b == NULL) {			\
	    free(b);				\
	    return NULL;			\
	}					\
	AP_RING_ELEM_INIT(ap__b, link);		\
	return ap__b;				\
    } while(0)


/**
 * Create an End of Stream bucket.  This indicates that there is no more data
 * coming from down the filter stack
 * @return The new bucket, or NULL if allocation failed
 * @deffunc ap_bucket *ap_bucket_create_eos(void)
 */
API_EXPORT(ap_bucket *) ap_bucket_create_eos(void);
API_EXPORT(ap_bucket *) ap_bucket_make_eos(ap_bucket *b);


/**
 * Create a bucket referring to long-lived data.
 * @param buf The data to insert into the bucket
 * @param nbyte The size of the data to insert.
 * @return The new bucket, or NULL if allocation failed
 * @deffunc ap_bucket *ap_bucket_create_transient(const char *buf, apr_size_t nbyte, apr_ssize_t *w)
 */
API_EXPORT(ap_bucket *) ap_bucket_create_immortal(
		const char *buf, apr_size_t nbyte);
API_EXPORT(ap_bucket *) ap_bucket_make_immortal(ap_bucket *b,
		const char *buf, apr_size_t nbyte);

/**
 * Create a bucket referring to data on the stack.
 * @param buf The data to insert into the bucket
 * @param nbyte The size of the data to insert.
 * @return The new bucket, or NULL if allocation failed
 * @deffunc ap_bucket *ap_bucket_create_transient(const char *buf, apr_size_t nbyte, apr_ssize_t *w)
 */
API_EXPORT(ap_bucket *) ap_bucket_create_transient(
		const char *buf, apr_size_t nbyte);
API_EXPORT(ap_bucket *) ap_bucket_make_transient(ap_bucket *b,
		const char *buf, apr_size_t nbyte);

/**
 * Create a bucket referring to memory on the heap. If the caller asks
 * for the data to be copied, this function always allocates 4K of
 * memory so that more data can be added to the bucket without
 * requiring another allocation. Therefore not all the data may be put
 * into the bucket. If copying is not requested then the bucket takes
 * over responsibility for free()ing the memory.
 * @param buf The buffer to insert into the bucket
 * @param nbyte The size of the buffer to insert.
 * @param copy Whether to copy the data into newly-allocated memory or not
 * @param w The number of bytes actually copied into the bucket.
 *          If copy is zero then this return value can be ignored by passing a NULL pointer.
 * @return The new bucket, or NULL if allocation failed
 * @deffunc ap_bucket *ap_bucket_create_heap(const char *buf, apr_size_t nbyte, int copy, apr_ssize_t *w)
 */
API_EXPORT(ap_bucket *) ap_bucket_create_heap(
		const char *buf, apr_size_t nbyte, int copy, apr_ssize_t *w);
API_EXPORT(ap_bucket *) ap_bucket_make_heap(ap_bucket *b,
		const char *buf, apr_size_t nbyte, int copy, apr_ssize_t *w);

/**
 * Create a bucket referring to mmap()ed memory.
 * @param mmap The mmap to insert into the bucket
 * @param start The offset of the first byte in the mmap
 *              that this bucket refers to
 * @param length The number of bytes referred to by this bucket
 * @return The new bucket, or NULL if allocation failed
 * @deffunc ap_bucket *ap_bucket_create_mmap(const apr_mmap_t *buf, apr_size_t nbyte, apr_ssize_t *w)
 */
API_EXPORT(ap_bucket *) ap_bucket_create_mmap(
		apr_mmap_t *mm, apr_off_t start, apr_size_t length);
API_EXPORT(ap_bucket *) ap_bucket_make_mmap(ap_bucket *b,
		apr_mmap_t *mm, apr_off_t start, apr_size_t length);

/**
 * Create a bucket referring to a pipe.
 * @param thispipe The pipe to put in the bucket
 * @return The new bucket, or NULL if allocation failed
 * @deffunc ap_bucket *ap_bucket_create_pipe(apr_file_t *thispipe)
 */
API_EXPORT(ap_bucket *) ap_bucket_create_pipe(apr_file_t *thispipe);
API_EXPORT(ap_bucket *) ap_bucket_make_pipe(ap_bucket *b, apr_file_t *thispipe);

/**
 * Create a bucket referring to a file.
 * @param fd The file to put in the bucket
 * @param offset The offset where the data of interest begins in the file
 * @param len The amount of data in the file we are interested in
 * @return The new bucket, or NULL if allocation failed
 * @deffunc ap_bucket *ap_bucket_create_file(apr_file_t *thispipe)
 */
API_EXPORT(ap_bucket *) ap_bucket_create_file(apr_file_t *fd, apr_off_t offset, apr_size_t len);
API_EXPORT(ap_bucket *) ap_bucket_make_file(ap_bucket *b, apr_file_t *fd, 
                                            apr_off_t offset, apr_size_t len);

#endif /* !AP_BUCKETS_H */