buffer.h

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/*
 *  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) 2002-2026 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, see <https://www.gnu.org/licenses/>.
 */
 
#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
 
/**************************************************************************/
struct buffer
{
    int capacity;  
    int offset;    
    int len;       
    uint8_t *data; 
#ifdef BUF_INIT_TRACKING
    const char *debug_file;
    int debug_line;
#endif
};
 
 
/**************************************************************************/
struct gc_entry
{
    struct gc_entry *next; 
};
 
struct gc_entry_special
{
    struct gc_entry_special *next;
    void (*free_fnc)(void *);
    void *addr;
};
 
 
struct gc_arena
{
    struct gc_entry *list; 
    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 BLENZ(buf) ((size_t)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);
 
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);
 
void *gc_realloc(void *ptr, size_t size, 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 */
static inline void
gc_freeaddrinfo_callback(void *addr)
{
    freeaddrinfo((struct addrinfo *)addr);
}
 
static inline struct buffer
clear_buf(void)
{
    return (struct buffer){ 0 };
}
 
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, size_t size)
{
    if (!buf_size_valid(size))
    {
        buf_size_error(size);
    }
    buf->len = buf->capacity = (int)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)
{
    if (maxlen > 0)
    {
        strncpy(dest, src, maxlen - 1);
        dest[maxlen - 1] = 0;
    }
}
 
/* return true if string contains at least one numerical digit */
static inline bool
has_digit(const char *src)
{
    char c;
    while ((c = *src++))
    {
        if (isdigit(c))
        {
            return true;
        }
    }
    return false;
}
 
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);
 
 
/*
 * 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);
 
bool buffer_write_file(const char *filename, const struct buffer *buf);
 
/*
 * write a string to the end of a buffer that was
 * truncated by buf_printf
 */
void buf_catrunc(struct buffer *buf, const char *str);
 
/*
 * 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, size_t size, size_t maxoutput, unsigned int space_break_flags,
                    const char *separator, struct gc_arena *gc);
 
static inline char *
format_hex(const uint8_t *data, size_t size, size_t 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, size_t len)
{
    return buf_valid(buf) && buf_size_valid(len)
           && buf->offset + buf->len + (int)len <= buf->capacity;
}
 
static inline bool
buf_safe_bidir(const struct buffer *buf, int len)
{
    if (buf_valid(buf) && buf_size_valid_signed(len))
    {
        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, ssize_t size)
{
    if (!buf_valid(buf) || size < 0 || size > buf->offset)
    {
        return NULL;
    }
    buf->offset -= (int)size;
    buf->len += (int)size;
    return BPTR(buf);
}
 
static inline bool
buf_advance(struct buffer *buf, ssize_t size)
{
    if (!buf_valid(buf) || size < 0 || buf->len < size)
    {
        return false;
    }
    buf->offset += (int)size;
    buf->len -= (int)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, size_t size)
{
    uint8_t *ret;
    if (!buf_safe(buf, size))
    {
        return NULL;
    }
    ret = BPTR(buf) + buf->len;
    buf->len += (int)size;
    return ret;
}
 
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, size_t 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, uint8_t data)
{
    return buf_write(dest, &data, sizeof(uint8_t));
}
 
static inline bool
buf_write_u16(struct buffer *dest, uint16_t data)
{
    uint16_t u16 = htons(data);
    return buf_write(dest, &u16, sizeof(uint16_t));
}
 
static inline bool
buf_write_u32(struct buffer *dest, uint32_t data)
{
    uint32_t u32 = htonl(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), BLENZ(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_peek_u8(struct buffer *buf)
{
    int ret;
    if (BLEN(buf) < 1)
    {
        return -1;
    }
    ret = *BPTR(buf);
    return ret;
}
 
static inline int
buf_read_u8(struct buffer *buf)
{
    int ret = buf_peek_u8(buf);
    if (ret >= 0)
    {
        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);
    }
}
 
static inline bool
buf_equal(const struct buffer *a, const struct buffer *b)
{
    return BLEN(a) == BLEN(b) && 0 == memcmp(BPTR(a), BPTR(b), BLENZ(a));
}
 
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;
}
 
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);
 
/* 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);
 
 
bool string_check_buf(struct buffer *buf, const unsigned int inclusive,
                      const unsigned int exclusive);
 
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);
 
static inline bool
strprefix(const char *str, const char *prefix)
{
    return 0 == strncmp(str, prefix, strlen(prefix));
}
 
bool checked_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
    ;
 
/*
 * 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
 */
 
/* When allocating arrays make sure we do not use a excessive amount
 * of memory.
 */
#if UINTPTR_MAX <= UINT32_MAX
/* 1 GB on 32bit systems, they usually can only allocate 2 GB for the
 * whole process.
 */
#define ALLOC_SIZE_MAX (1u << 30)
#else
#define ALLOC_SIZE_MAX ((size_t)1 << 32) /* 4 GB */
#endif
 
#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(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 */
};
 
struct buffer_list *buffer_list_new(void);
 
void buffer_list_free(struct buffer_list *ol);
 
bool buffer_list_defined(const struct buffer_list *ol);
 
void buffer_list_reset(struct buffer_list *ol);
 
void buffer_list_push(struct buffer_list *ol, const char *str);
 
struct buffer_entry *buffer_list_push_data(struct buffer_list *ol, const void *data, size_t size);
 
struct buffer *buffer_list_peek(struct buffer_list *ol);
 
void buffer_list_advance(struct buffer_list *ol, ssize_t n);
 
void buffer_list_pop(struct buffer_list *ol);
 
void buffer_list_aggregate(struct buffer_list *bl, const size_t max);
 
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);
 
struct buffer buffer_read_from_file(const char *filename, struct gc_arena *gc);
 
#endif /* BUFFER_H */