/*
 *  OpenVPN -- An application to securely tunnel IP networks
 *             over a single UDP port, with support for SSL/TLS-based
 *             session authentication and key exchange,
 *             packet encryption, packet authentication, and
 *             packet compression.
 *
 *  Copyright (C) 2002-2018 OpenVPN Inc <sales@openvpn.net>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2
 *  as published by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#ifndef BUFFER_H
#define BUFFER_H

#include "basic.h"
#include "error.h"

#define BUF_SIZE_MAX 1000000

/*
 * Define verify_align function, otherwise
 * it will be a noop.
 */
/* #define VERIFY_ALIGNMENT */

/*
 * Keep track of source file/line of buf_init calls
 */
#ifdef VERIFY_ALIGNMENT
#define BUF_INIT_TRACKING
#endif

/**************************************************************************/
/**
 * Wrapper structure for dynamically allocated memory.
 *
 * The actual content stored in a \c buffer structure starts at the memory
 * location \c buffer.data \c + \c buffer.offset, and has a length of \c
 * buffer.len bytes.  This, together with the space available before and
 * after the content, is represented in the pseudocode below:
 * @code
 * uint8_t *content_start    = buffer.data + buffer.offset;
 * uint8_t *content_end      = buffer.data + buffer.offset + buffer.len;
 * int      prepend_capacity = buffer.offset;
 * int      append_capacity  = buffer.capacity - (buffer.offset + buffer.len);
 * @endcode
 */
struct buffer
{
    int capacity;               /**< Size in bytes of memory allocated by
                                 *   \c malloc(). */
    int offset;                 /**< Offset in bytes of the actual content
                                 *   within the allocated memory. */
    int len;                    /**< Length in bytes of the actual content
                                 *   within the allocated memory. */
    uint8_t *data;              /**< Pointer to the allocated memory. */

#ifdef BUF_INIT_TRACKING
    const char *debug_file;
    int debug_line;
#endif
};


/**************************************************************************/
/**
 * Garbage collection entry for one dynamically allocated block of memory.
 *
 * This structure represents one link in the linked list contained in a \c
 * gc_arena structure.  Each time the \c gc_malloc() function is called,
 * it allocates \c sizeof(gc_entry) + the requested number of bytes.  The
 * \c gc_entry is then stored as a header in front of the memory address
 * returned to the caller.
 */
struct gc_entry
{
    struct gc_entry *next;      /**< Pointer to the next item in the
                                 *   linked list. */
};

/**
 * Garbage collection entry for a specially allocated structure that needs
 * a custom free function to be freed like struct addrinfo
 *
 */
struct gc_entry_special
{
    struct gc_entry_special *next;
    void (*free_fnc)(void *);
    void *addr;
};


/**
 * Garbage collection arena used to keep track of dynamically allocated
 * memory.
 *
 * This structure contains a linked list of \c gc_entry structures.  When
 * a block of memory is allocated using the \c gc_malloc() function, the
 * allocation is registered in the function's \c gc_arena argument.  All
 * the dynamically allocated memory registered in a \c gc_arena can be
 * freed using the \c gc_free() function.
 */
struct gc_arena
{
    struct gc_entry *list;      /**< First element of the linked list of
                                 *   \c gc_entry structures. */
    struct gc_entry_special *list_special;
};


#define BPTR(buf)  (buf_bptr(buf))
#define BEND(buf)  (buf_bend(buf))
#define BLAST(buf) (buf_blast(buf))
#define BLEN(buf)  (buf_len(buf))
#define BDEF(buf)  (buf_defined(buf))
#define BSTR(buf)  (buf_str(buf))
#define BCAP(buf)  (buf_forward_capacity(buf))

void buf_clear(struct buffer *buf);

struct buffer clear_buf(void);

void free_buf(struct buffer *buf);

bool buf_assign(struct buffer *dest, const struct buffer *src);

void string_clear(char *str);

int string_array_len(const char **array);

size_t array_mult_safe(const size_t m1, const size_t m2, const size_t extra);

#define PA_BRACKET (1<<0)
char *print_argv(const char **p, struct gc_arena *gc, const unsigned int flags);

void buf_size_error(const size_t size);

/* for dmalloc debugging */

#ifdef DMALLOC

#define alloc_buf(size)               alloc_buf_debug(size, __FILE__, __LINE__)
#define alloc_buf_gc(size, gc)        alloc_buf_gc_debug(size, gc, __FILE__, __LINE__);
#define clone_buf(buf)                clone_buf_debug(buf, __FILE__, __LINE__);
#define gc_malloc(size, clear, arena) gc_malloc_debug(size, clear, arena, __FILE__, __LINE__)
#define string_alloc(str, gc)         string_alloc_debug(str, gc, __FILE__, __LINE__)
#define string_alloc_buf(str, gc)     string_alloc_buf_debug(str, gc, __FILE__, __LINE__)

struct buffer alloc_buf_debug(size_t size, const char *file, int line);

struct buffer alloc_buf_gc_debug(size_t size, struct gc_arena *gc, const char *file, int line);

struct buffer clone_buf_debug(const struct buffer *buf, const char *file, int line);

void *gc_malloc_debug(size_t size, bool clear, struct gc_arena *a, const char *file, int line);

char *string_alloc_debug(const char *str, struct gc_arena *gc, const char *file, int line);

struct buffer string_alloc_buf_debug(const char *str, struct gc_arena *gc, const char *file, int line);

#else  /* ifdef DMALLOC */

struct buffer alloc_buf(size_t size);

struct buffer alloc_buf_gc(size_t size, struct gc_arena *gc);  /* allocate buffer with garbage collection */

struct buffer clone_buf(const struct buffer *buf);

void *gc_malloc(size_t size, bool clear, struct gc_arena *a);

char *string_alloc(const char *str, struct gc_arena *gc);

struct buffer string_alloc_buf(const char *str, struct gc_arena *gc);

#endif /* ifdef DMALLOC */

void gc_addspecial(void *addr, void (*free_function)(void *), struct gc_arena *a);


#ifdef BUF_INIT_TRACKING
#define buf_init(buf, offset) buf_init_debug(buf, offset, __FILE__, __LINE__)
bool buf_init_debug(struct buffer *buf, int offset, const char *file, int line);

#else
#define buf_init(buf, offset) buf_init_dowork(buf, offset)
#endif


/* inline functions */
inline static void
gc_freeaddrinfo_callback(void *addr)
{
    freeaddrinfo((struct addrinfo *) addr);
}

static inline bool
buf_defined(const struct buffer *buf)
{
    return buf->data != NULL;
}

static inline bool
buf_valid(const struct buffer *buf)
{
    return likely(buf->data != NULL) && likely(buf->len >= 0);
}

static inline uint8_t *
buf_bptr(const struct buffer *buf)
{
    if (buf_valid(buf))
    {
        return buf->data + buf->offset;
    }
    else
    {
        return NULL;
    }
}

static int
buf_len(const struct buffer *buf)
{
    if (buf_valid(buf))
    {
        return buf->len;
    }
    else
    {
        return 0;
    }
}

static inline uint8_t *
buf_bend(const struct buffer *buf)
{
    return buf_bptr(buf) + buf_len(buf);
}

static inline uint8_t *
buf_blast(const struct buffer *buf)
{
    if (buf_len(buf) > 0)
    {
        return buf_bptr(buf) + buf_len(buf) - 1;
    }
    else
    {
        return NULL;
    }
}

static inline bool
buf_size_valid(const size_t size)
{
    return likely(size < BUF_SIZE_MAX);
}

static inline bool
buf_size_valid_signed(const int size)
{
    return likely(size >= -BUF_SIZE_MAX) && likely(size < BUF_SIZE_MAX);
}

static inline char *
buf_str(const struct buffer *buf)
{
    return (char *)buf_bptr(buf);
}

static inline void
buf_reset(struct buffer *buf)
{
    buf->capacity = 0;
    buf->offset = 0;
    buf->len = 0;
    buf->data = NULL;
}

static inline void
buf_reset_len(struct buffer *buf)
{
    buf->len = 0;
    buf->offset = 0;
}

static inline bool
buf_init_dowork(struct buffer *buf, int offset)
{
    if (offset < 0 || offset > buf->capacity || buf->data == NULL)
    {
        return false;
    }
    buf->len = 0;
    buf->offset = offset;
    return true;
}

static inline void
buf_set_write(struct buffer *buf, uint8_t *data, int size)
{
    if (!buf_size_valid(size))
    {
        buf_size_error(size);
    }
    buf->len = 0;
    buf->offset = 0;
    buf->capacity = size;
    buf->data = data;
    if (size > 0 && data)
    {
        *data = 0;
    }
}

static inline void
buf_set_read(struct buffer *buf, const uint8_t *data, int size)
{
    if (!buf_size_valid(size))
    {
        buf_size_error(size);
    }
    buf->len = buf->capacity = size;
    buf->offset = 0;
    buf->data = (uint8_t *)data;
}

/* Like strncpy but makes sure dest is always null terminated */
static inline void
strncpynt(char *dest, const char *src, size_t maxlen)
{
    strncpy(dest, src, maxlen);
    if (maxlen > 0)
    {
        dest[maxlen - 1] = 0;
    }
}

/* return true if string contains at least one numerical digit */
static inline bool
has_digit(const unsigned char *src)
{
    unsigned char c;
    while ((c = *src++))
    {
        if (isdigit(c))
        {
            return true;
        }
    }
    return false;
}

/**
 * Securely zeroise memory.
 *
 * This code and description are based on code supplied by Zhaomo Yang, of the
 * University of California, San Diego (which was released into the public
 * domain).
 *
 * The secure_memzero function attempts to ensure that an optimizing compiler
 * does not remove the intended operation if cleared memory is not accessed
 * again by the program. This code has been tested under Clang 3.9.0 and GCC
 * 6.2 with optimization flags -O, -Os, -O0, -O1, -O2, and -O3 on
 * Ubuntu 16.04.1 LTS; under Clang 3.9.0 with optimization flags -O, -Os,
 * -O0, -O1, -O2, and -O3 on FreeBSD 10.2-RELEASE; under Microsoft Visual Studio
 * 2015 with optimization flags /O1, /O2 and /Ox on Windows 10.
 *
 * Theory of operation:
 *
 * 1. On Windows, use the SecureZeroMemory which ensures that data is
 *    overwritten.
 * 2. Under GCC or Clang, use a memory barrier, which forces the preceding
 *    memset to be carried out. The overhead of a memory barrier is usually
 *    negligible.
 * 3. If none of the above are available, use the volatile pointer
 *    technique to zero memory one byte at a time.
 *
 * @param data  Pointer to data to zeroise.
 * @param len   Length of data, in bytes.
 */
static inline void
secure_memzero(void *data, size_t len)
{
#if defined(_WIN32)
    SecureZeroMemory(data, len);
#elif defined(__GNUC__) || defined(__clang__)
    memset(data, 0, len);
    __asm__ __volatile__ ("" : : "r" (data) : "memory");
#else
    volatile char *p = (volatile char *) data;
    while (len--)
    {
        *p++ = 0;
    }
#endif
}

/*
 * printf append to a buffer with overflow check,
 * due to usage of vsnprintf, it will leave space for
 * a final null character and thus use only
 * capacity - 1
 */
bool buf_printf(struct buffer *buf, const char *format, ...)
#ifdef __GNUC__
#if __USE_MINGW_ANSI_STDIO
__attribute__ ((format(gnu_printf, 2, 3)))
#else
__attribute__ ((format(__printf__, 2, 3)))
#endif
#endif
;

/*
 * puts append to a buffer with overflow check
 */
bool buf_puts(struct buffer *buf, const char *str);

/*
 * Like snprintf but guarantees null termination for size > 0
 */
bool openvpn_snprintf(char *str, size_t size, const char *format, ...)
#ifdef __GNUC__
#if __USE_MINGW_ANSI_STDIO
__attribute__ ((format(gnu_printf, 3, 4)))
#else
__attribute__ ((format(__printf__, 3, 4)))
#endif
#endif
;

/*
 * remove/add trailing characters
 */

void buf_null_terminate(struct buffer *buf);

void buf_chomp(struct buffer *buf);

void buf_rmtail(struct buffer *buf, uint8_t remove);

/*
 * non-buffer string functions
 */
void chomp(char *str);

void rm_trailing_chars(char *str, const char *what_to_delete);

const char *skip_leading_whitespace(const char *str);

void string_null_terminate(char *str, int len, int capacity);

/*
 * Write string in buf to file descriptor fd.
 * NOTE: requires that string be null terminated.
 */
void buf_write_string_file(const struct buffer *buf, const char *filename, int fd);

/*
 * write a string to the end of a buffer that was
 * truncated by buf_printf
 */
void buf_catrunc(struct buffer *buf, const char *str);

/*
 * convert a multi-line output to one line
 */
void convert_to_one_line(struct buffer *buf);

/*
 * Parse a string based on a given delimiter char
 */
bool buf_parse(struct buffer *buf, const int delim, char *line, const int size);

/*
 * Hex dump -- Output a binary buffer to a hex string and return it.
 */
#define FHE_SPACE_BREAK_MASK 0xFF /* space_break parameter in lower 8 bits */
#define FHE_CAPS 0x100            /* output hex in caps */
char *
format_hex_ex(const uint8_t *data, int size, int maxoutput,
              unsigned int space_break_flags, const char *separator,
              struct gc_arena *gc);

static inline char *
format_hex(const uint8_t *data, int size, int maxoutput, struct gc_arena *gc)
{
    return format_hex_ex(data, size, maxoutput, 4, " ", gc);
}

/*
 * Return a buffer that is a subset of another buffer.
 */
struct buffer buf_sub(struct buffer *buf, int size, bool prepend);

/*
 * Check if sufficient space to append to buffer.
 */

static inline bool
buf_safe(const struct buffer *buf, int len)
{
    return buf_valid(buf) && buf_size_valid(len)
           && buf->offset + buf->len + len <= buf->capacity;
}

static inline bool
buf_safe_bidir(const struct buffer *buf, int len)
{
    if (buf_valid(buf) && buf_size_valid_signed(len))
    {
        const int newlen = buf->len + len;
        return newlen >= 0 && buf->offset + newlen <= buf->capacity;
    }
    else
    {
        return false;
    }
}

static inline int
buf_forward_capacity(const struct buffer *buf)
{
    if (buf_valid(buf))
    {
        int ret = buf->capacity - (buf->offset + buf->len);
        if (ret < 0)
        {
            ret = 0;
        }
        return ret;
    }
    else
    {
        return 0;
    }
}

static inline int
buf_forward_capacity_total(const struct buffer *buf)
{
    if (buf_valid(buf))
    {
        int ret = buf->capacity - buf->offset;
        if (ret < 0)
        {
            ret = 0;
        }
        return ret;
    }
    else
    {
        return 0;
    }
}

static inline int
buf_reverse_capacity(const struct buffer *buf)
{
    if (buf_valid(buf))
    {
        return buf->offset;
    }
    else
    {
        return 0;
    }
}

static inline bool
buf_inc_len(struct buffer *buf, int inc)
{
    if (!buf_safe_bidir(buf, inc))
    {
        return false;
    }
    buf->len += inc;
    return true;
}

/*
 * Make space to prepend to a buffer.
 * Return NULL if no space.
 */

static inline uint8_t *
buf_prepend(struct buffer *buf, int size)
{
    if (!buf_valid(buf) || size < 0 || size > buf->offset)
    {
        return NULL;
    }
    buf->offset -= size;
    buf->len += size;
    return BPTR(buf);
}

static inline bool
buf_advance(struct buffer *buf, int size)
{
    if (!buf_valid(buf) || size < 0 || buf->len < size)
    {
        return false;
    }
    buf->offset += size;
    buf->len -= size;
    return true;
}

/*
 * Return a pointer to allocated space inside a buffer.
 * Return NULL if no space.
 */

static inline uint8_t *
buf_write_alloc(struct buffer *buf, int size)
{
    uint8_t *ret;
    if (!buf_safe(buf, size))
    {
        return NULL;
    }
    ret = BPTR(buf) + buf->len;
    buf->len += size;
    return ret;
}

static inline uint8_t *
buf_write_alloc_prepend(struct buffer *buf, int size, bool prepend)
{
    return prepend ? buf_prepend(buf, size) : buf_write_alloc(buf, size);
}

static inline uint8_t *
buf_read_alloc(struct buffer *buf, int size)
{
    uint8_t *ret;
    if (size < 0 || buf->len < size)
    {
        return NULL;
    }
    ret = BPTR(buf);
    buf->offset += size;
    buf->len -= size;
    return ret;
}

static inline bool
buf_write(struct buffer *dest, const void *src, int size)
{
    uint8_t *cp = buf_write_alloc(dest, size);
    if (!cp)
    {
        return false;
    }
    memcpy(cp, src, size);
    return true;
}

static inline bool
buf_write_prepend(struct buffer *dest, const void *src, int size)
{
    uint8_t *cp = buf_prepend(dest, size);
    if (!cp)
    {
        return false;
    }
    memcpy(cp, src, size);
    return true;
}

static inline bool
buf_write_u8(struct buffer *dest, int data)
{
    uint8_t u8 = (uint8_t) data;
    return buf_write(dest, &u8, sizeof(uint8_t));
}

static inline bool
buf_write_u16(struct buffer *dest, int data)
{
    uint16_t u16 = htons((uint16_t) data);
    return buf_write(dest, &u16, sizeof(uint16_t));
}

static inline bool
buf_write_u32(struct buffer *dest, int data)
{
    uint32_t u32 = htonl((uint32_t) data);
    return buf_write(dest, &u32, sizeof(uint32_t));
}

static inline bool
buf_copy(struct buffer *dest, const struct buffer *src)
{
    return buf_write(dest, BPTR(src), BLEN(src));
}

static inline bool
buf_copy_n(struct buffer *dest, struct buffer *src, int n)
{
    uint8_t *cp = buf_read_alloc(src, n);
    if (!cp)
    {
        return false;
    }
    return buf_write(dest, cp, n);
}

static inline bool
buf_copy_range(struct buffer *dest,
               int dest_index,
               const struct buffer *src,
               int src_index,
               int src_len)
{
    if (src_index < 0
        || src_len < 0
        || src_index + src_len > src->len
        || dest_index < 0
        || dest->offset + dest_index + src_len > dest->capacity)
    {
        return false;
    }
    memcpy(dest->data + dest->offset + dest_index, src->data + src->offset + src_index, src_len);
    if (dest_index + src_len > dest->len)
    {
        dest->len = dest_index + src_len;
    }
    return true;
}

/* truncate src to len, copy excess data beyond len to dest */
static inline bool
buf_copy_excess(struct buffer *dest,
                struct buffer *src,
                int len)
{
    if (len < 0)
    {
        return false;
    }
    if (src->len > len)
    {
        struct buffer b = *src;
        src->len = len;
        if (!buf_advance(&b, len))
        {
            return false;
        }
        return buf_copy(dest, &b);
    }
    else
    {
        return true;
    }
}

static inline bool
buf_read(struct buffer *src, void *dest, int size)
{
    uint8_t *cp = buf_read_alloc(src, size);
    if (!cp)
    {
        return false;
    }
    memcpy(dest, cp, size);
    return true;
}

static inline int
buf_read_u8(struct buffer *buf)
{
    int ret;
    if (BLEN(buf) < 1)
    {
        return -1;
    }
    ret = *BPTR(buf);
    buf_advance(buf, 1);
    return ret;
}

static inline int
buf_read_u16(struct buffer *buf)
{
    uint16_t ret;
    if (!buf_read(buf, &ret, sizeof(uint16_t)))
    {
        return -1;
    }
    return ntohs(ret);
}

static inline uint32_t
buf_read_u32(struct buffer *buf, bool *good)
{
    uint32_t ret;
    if (!buf_read(buf, &ret, sizeof(uint32_t)))
    {
        if (good)
        {
            *good = false;
        }
        return 0;
    }
    else
    {
        if (good)
        {
            *good = true;
        }
        return ntohl(ret);
    }
}

/**
 * Compare src buffer contents with match.
 * *NOT* constant time. Do not use when comparing HMACs.
 */
static inline bool
buf_string_match(const struct buffer *src, const void *match, int size)
{
    if (size != src->len)
    {
        return false;
    }
    return memcmp(BPTR(src), match, size) == 0;
}

/**
 * Compare first size bytes of src buffer contents with match.
 * *NOT* constant time. Do not use when comparing HMACs.
 */
static inline bool
buf_string_match_head(const struct buffer *src, const void *match, int size)
{
    if (size < 0 || size > src->len)
    {
        return false;
    }
    return memcmp(BPTR(src), match, size) == 0;
}

bool buf_string_match_head_str(const struct buffer *src, const char *match);

bool buf_string_compare_advance(struct buffer *src, const char *match);

int buf_substring_len(const struct buffer *buf, int delim);

/*
 * Print a string which might be NULL
 */
const char *np(const char *str);

/*#define CHARACTER_CLASS_DEBUG*/

/* character classes */

#define CC_ANY                (1<<0)
#define CC_NULL               (1<<1)

#define CC_ALNUM              (1<<2)
#define CC_ALPHA              (1<<3)
#define CC_ASCII              (1<<4)
#define CC_CNTRL              (1<<5)
#define CC_DIGIT              (1<<6)
#define CC_PRINT              (1<<7)
#define CC_PUNCT              (1<<8)
#define CC_SPACE              (1<<9)
#define CC_XDIGIT             (1<<10)

#define CC_BLANK              (1<<11)
#define CC_NEWLINE            (1<<12)
#define CC_CR                 (1<<13)

#define CC_BACKSLASH          (1<<14)
#define CC_UNDERBAR           (1<<15)
#define CC_DASH               (1<<16)
#define CC_DOT                (1<<17)
#define CC_COMMA              (1<<18)
#define CC_COLON              (1<<19)
#define CC_SLASH              (1<<20)
#define CC_SINGLE_QUOTE       (1<<21)
#define CC_DOUBLE_QUOTE       (1<<22)
#define CC_REVERSE_QUOTE      (1<<23)
#define CC_AT                 (1<<24)
#define CC_EQUAL              (1<<25)
#define CC_LESS_THAN          (1<<26)
#define CC_GREATER_THAN       (1<<27)
#define CC_PIPE               (1<<28)
#define CC_QUESTION_MARK      (1<<29)
#define CC_ASTERISK           (1<<30)

/* macro classes */
#define CC_NAME               (CC_ALNUM|CC_UNDERBAR)
#define CC_CRLF               (CC_CR|CC_NEWLINE)

bool char_class(const unsigned char c, const unsigned int flags);

bool string_class(const char *str, const unsigned int inclusive, const unsigned int exclusive);

bool string_mod(char *str, const unsigned int inclusive, const unsigned int exclusive, const char replace);

const char *string_mod_const(const char *str,
                             const unsigned int inclusive,
                             const unsigned int exclusive,
                             const char replace,
                             struct gc_arena *gc);

void string_replace_leading(char *str, const char match, const char replace);

/** Return true iff str starts with prefix */
static inline bool
strprefix(const char *str, const char *prefix)
{
    return 0 == strncmp(str, prefix, strlen(prefix));
}


#ifdef CHARACTER_CLASS_DEBUG
void character_class_debug(void);

#endif

/*
 * Verify that a pointer is correctly aligned
 */
#ifdef VERIFY_ALIGNMENT
void valign4(const struct buffer *buf, const char *file, const int line);

#define verify_align_4(ptr) valign4(buf, __FILE__, __LINE__)
#else
#define verify_align_4(ptr)
#endif

/*
 * Very basic garbage collection, mostly for routines that return
 * char ptrs to malloced strings.
 */

void gc_transfer(struct gc_arena *dest, struct gc_arena *src);

void x_gc_free(struct gc_arena *a);

void x_gc_freespecial(struct gc_arena *a);

static inline bool
gc_defined(struct gc_arena *a)
{
    return a->list != NULL;
}

static inline void
gc_init(struct gc_arena *a)
{
    a->list = NULL;
    a->list_special = NULL;
}

static inline void
gc_detach(struct gc_arena *a)
{
    gc_init(a);
}

static inline struct gc_arena
gc_new(void)
{
    struct gc_arena ret;
    gc_init(&ret);
    return ret;
}

static inline void
gc_free(struct gc_arena *a)
{
    if (a->list)
    {
        x_gc_free(a);
    }
    if (a->list_special)
    {
        x_gc_freespecial(a);
    }
}

static inline void
gc_reset(struct gc_arena *a)
{
    gc_free(a);
}

/*
 * Allocate memory to hold a structure
 */

#define ALLOC_OBJ(dptr, type) \
    { \
        check_malloc_return((dptr) = (type *) malloc(sizeof(type))); \
    }

#define ALLOC_OBJ_CLEAR(dptr, type) \
    { \
        ALLOC_OBJ(dptr, type); \
        memset((dptr), 0, sizeof(type)); \
    }

#define ALLOC_ARRAY(dptr, type, n) \
    { \
        check_malloc_return((dptr) = (type *) malloc(array_mult_safe(sizeof(type), (n), 0))); \
    }

#define ALLOC_ARRAY_GC(dptr, type, n, gc) \
    { \
        (dptr) = (type *) gc_malloc(array_mult_safe(sizeof(type), (n), 0), false, (gc)); \
    }

#define ALLOC_ARRAY_CLEAR(dptr, type, n) \
    { \
        ALLOC_ARRAY(dptr, type, n); \
        memset((dptr), 0, (array_mult_safe(sizeof(type), (n), 0))); \
    }

#define ALLOC_ARRAY_CLEAR_GC(dptr, type, n, gc) \
    { \
        (dptr) = (type *) gc_malloc(array_mult_safe(sizeof(type), (n), 0), true, (gc)); \
    }

#define ALLOC_VAR_ARRAY_CLEAR_GC(dptr, type, atype, n, gc)      \
    { \
        (dptr) = (type *) gc_malloc(array_mult_safe(sizeof(atype), (n), sizeof(type)), true, (gc)); \
    }

#define ALLOC_OBJ_GC(dptr, type, gc) \
    { \
        (dptr) = (type *) gc_malloc(sizeof(type), false, (gc)); \
    }

#define ALLOC_OBJ_CLEAR_GC(dptr, type, gc) \
    { \
        (dptr) = (type *) gc_malloc(sizeof(type), true, (gc)); \
    }

static inline void
check_malloc_return(const void *p)
{
    if (!p)
    {
        out_of_memory();
    }
}

/*
 * Manage lists of buffers
 */
struct buffer_entry
{
    struct buffer buf;
    struct buffer_entry *next;
};

struct buffer_list
{
    struct buffer_entry *head; /* next item to pop/peek */
    struct buffer_entry *tail; /* last item pushed */
    int size;                /* current number of entries */
    int max_size;            /* maximum size list should grow to */
};

/**
 * Allocate an empty buffer list of capacity \c max_size.
 *
 * @param max_size  the capacity of the list to allocate
 *
 * @return the new list
 */
struct buffer_list *buffer_list_new(const int max_size);

/**
 * Frees a buffer list and all the buffers in it.
 *
 * @param ol    the list to free
 */
void buffer_list_free(struct buffer_list *ol);

/**
 * Checks if the list is valid and non-empty
 *
 * @param ol    the list to check
 *
 * @return true iff \c ol is not NULL and contains at least one buffer
 */
bool buffer_list_defined(const struct buffer_list *ol);

/**
 * Empty the list \c ol and frees all the contained buffers
 *
 * @param ol    the list to reset
 */
void buffer_list_reset(struct buffer_list *ol);

/**
 * Allocates and appends a new buffer containing \c str as data to \c ol
 *
 * @param ol    the list to append the new buffer to
 * @param str   the string to copy into the new buffer
 */
void buffer_list_push(struct buffer_list *ol, const char *str);

/**
 * Allocates and appends a new buffer containing \c data of length \c size.
 *
 * @param ol    the list to append the new buffer to
 * @param data  the data to copy into the new buffer
 * @param size  the length of \c data to copy into the buffer
 *
 * @return the new buffer
 */
struct buffer_entry *buffer_list_push_data(struct buffer_list *ol, const void *data, size_t size);

/**
 * Retrieve the head buffer
 *
 * @param ol    the list to retrieve the buffer from
 *
 * @return a pointer to the head buffer or NULL if the list is empty
 */
struct buffer *buffer_list_peek(struct buffer_list *ol);

void buffer_list_advance(struct buffer_list *ol, int n);

void buffer_list_pop(struct buffer_list *ol);

/**
 * Aggregates as many buffers as possible from \c bl in a new buffer of maximum
 * length \c max_len .
 * All the aggregated buffers are removed from the list and replaced by the new
 * one, followed by any additional (non-aggregated) data.
 *
 * @param bl    the list of buffer to aggregate
 * @param max   the maximum length of the aggregated buffer
 */
void buffer_list_aggregate(struct buffer_list *bl, const size_t max);

/**
 * Aggregates as many buffers as possible from \c bl in a new buffer
 * of maximum length \c max_len . \c sep is written after
 * each copied buffer (also after the last one). All the aggregated buffers are
 * removed from the list and replaced by the new one, followed by any additional
 * (non-aggregated) data.
 * Nothing happens if \c max_len is not enough to aggregate at least 2 buffers.
 *
 * @param bl        the list of buffer to aggregate
 * @param max_len   the maximum length of the aggregated buffer
 * @param sep       the separator to put between buffers during aggregation
 */
void buffer_list_aggregate_separator(struct buffer_list *bl,
                                     const size_t max_len, const char *sep);

struct buffer_list *buffer_list_file(const char *fn, int max_line_len);

#endif /* BUFFER_H */