Data-Buffer-Shared

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buf_generic.h  view on Meta::CPAN


#ifndef BUF_DEFS_H
#define BUF_DEFS_H

#include <stdint.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/file.h>
#include <sys/syscall.h>
#include <limits.h>
#include <signal.h>
#include <errno.h>
#include <linux/futex.h>
#include <sys/eventfd.h>
#include <pthread.h>

/* ---- Constants ---- */

#define BUF_MAGIC       0x42554631U  /* "BUF1" */
#define BUF_VERSION     2            /* v2: reader-slot table for dead-reader rwlock recovery */
#define BUF_ERR_BUFLEN  256
#define BUF_READER_SLOTS 1024         /* per-process reader-counter mirror */

/* ---- Per-process reader-slot table (in shared memory) ----
 * Mirrors each process's contribution to the global rwlock counters so a
 * dead reader's contribution can be reclaimed on writer-lock timeout. */
typedef struct {
    uint32_t pid;             /* owning PID, 0 = free */
    uint32_t subcount;        /* this process's rwlock reader contribution */
    uint32_t waiters_parked;  /* this process's contribution to rwlock_waiters */
    uint32_t writers_parked;  /* this process's contribution to rwlock_writers_waiting */
} BufReaderSlot;

/* ---- Shared memory header (128 bytes, 2 cache lines, in mmap) ---- */

#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
#define BUF_STATIC_ASSERT(cond, msg) _Static_assert(cond, msg)
#else
#define BUF_STATIC_ASSERT(cond, msg)
#endif

typedef struct {
    /* ---- Cache line 0 (0-63): immutable after create ---- */
    uint32_t magic;           /* 0 */
    uint32_t version;         /* 4 */
    uint32_t variant_id;      /* 8 */
    uint32_t elem_size;       /* 12 */
    uint64_t capacity;        /* 16: number of elements */
    uint64_t total_size;      /* 24: total mmap size */
    uint64_t data_off;        /* 32: offset to data array */
    uint64_t reader_slots_off;/* 40: offset to BufReaderSlot[BUF_READER_SLOTS] */
    uint8_t  _reserved0[16];  /* 48-63 */

    /* ---- Cache line 1 (64-127): seqlock + rwlock + mutable state ---- */
    uint32_t seq;             /* 64: seqlock counter, odd = writer active */
    uint32_t rwlock;          /* 68: 0=unlocked, readers=1..0x7FFFFFFF, writer=0x80000000|pid */
    uint32_t rwlock_waiters;  /* 72: wake-target counter (readers+writers) */
    uint32_t stat_recoveries; /* 76 */
    uint32_t rwlock_writers_waiting; /* 80: reader yield signal (writers only) */
    uint32_t _pad2;           /* 84 */
    uint64_t _reserved1[5];   /* 88-127 */
} BufHeader;

BUF_STATIC_ASSERT(sizeof(BufHeader) == 128, "BufHeader must be exactly 128 bytes (2 cache lines)");

/* ---- Process-local handle ---- */

typedef struct {
    BufHeader *hdr;
    void      *data;         /* pointer to element array in mmap */
    BufReaderSlot *reader_slots; /* in mmap, BUF_READER_SLOTS entries */
    size_t     mmap_size;
    char      *path;         /* backing file path (strdup'd, NULL for anon) */
    int        fd;           /* kept open for memfd, -1 otherwise */
    int        efd;          /* eventfd for notifications, -1 if none */
    uint32_t   my_slot_idx;  /* UINT32_MAX = unclaimed; per-process slot index */
    uint32_t   cached_pid;   /* getpid() at claim time */
    uint32_t   cached_fork_gen; /* fork-generation at claim time */
    uint8_t    wr_locked;    /* process-local: 1 if lock_wr is held */
    uint8_t    efd_owned;    /* 1 if we created the eventfd (close on destroy) */
} BufHandle;

/* ---- Futex-based read-write lock ---- */

#define BUF_RWLOCK_SPIN_LIMIT 32
#define BUF_LOCK_TIMEOUT_SEC  2

static inline void buf_spin_pause(void) {
#if defined(__x86_64__) || defined(__i386__)
    __asm__ volatile("pause" ::: "memory");
#elif defined(__aarch64__)
    __asm__ volatile("yield" ::: "memory");
#else
    __asm__ volatile("" ::: "memory");
#endif
}

#define BUF_RWLOCK_WRITER_BIT 0x80000000U
#define BUF_RWLOCK_PID_MASK   0x7FFFFFFFU
#define BUF_RWLOCK_WR(pid)    (BUF_RWLOCK_WRITER_BIT | ((uint32_t)(pid) & BUF_RWLOCK_PID_MASK))

static inline int buf_pid_alive(uint32_t pid) {
    if (pid == 0) return 1;
    return !(kill((pid_t)pid, 0) == -1 && errno == ESRCH);
}

/* ---- Per-process slot lifecycle (dead-reader recovery) ----
 * Each process claims one BufReaderSlot lazily on first lock op so that
 * its contribution to the shared rwlock counter can be reclaimed by other
 * processes if it dies (SIGKILL'd worker no longer pins the counter). */
static uint32_t buf_fork_gen = 0;
static pthread_once_t buf_atfork_once = PTHREAD_ONCE_INIT;
static void buf_on_fork_child(void) {
    __atomic_add_fetch(&buf_fork_gen, 1, __ATOMIC_RELAXED);
}
static void buf_atfork_init(void) {
    pthread_atfork(NULL, NULL, buf_on_fork_child);
}

static inline void buf_claim_reader_slot(BufHandle *h) {
    if (!h->reader_slots) return;
    pthread_once(&buf_atfork_once, buf_atfork_init);
    uint32_t cur_gen = __atomic_load_n(&buf_fork_gen, __ATOMIC_RELAXED);
    if (h->cached_fork_gen != cur_gen) {
        h->cached_fork_gen = cur_gen;
        h->my_slot_idx = UINT32_MAX;
    }
    if (h->my_slot_idx != UINT32_MAX) return;
    uint32_t now_pid = (uint32_t)getpid();
    h->cached_pid = now_pid;
    uint32_t start = now_pid % BUF_READER_SLOTS;
    for (uint32_t i = 0; i < BUF_READER_SLOTS; i++) {
        uint32_t s = (start + i) % BUF_READER_SLOTS;
        uint32_t expected = 0;
        if (__atomic_compare_exchange_n(&h->reader_slots[s].pid,
                &expected, now_pid, 0,
                __ATOMIC_ACQUIRE, __ATOMIC_RELAXED)) {
            __atomic_store_n(&h->reader_slots[s].subcount, 0, __ATOMIC_RELAXED);
            __atomic_store_n(&h->reader_slots[s].waiters_parked, 0, __ATOMIC_RELAXED);

buf_generic.h  view on Meta::CPAN

 * ================================================================ */

#ifndef BUF_PREFIX
#error "BUF_PREFIX must be defined before including buf_generic.h"
#endif

#define BUF_PASTE2(a, b) a##_##b
#define BUF_PASTE(a, b)  BUF_PASTE2(a, b)
#define BUF_FN(name)     BUF_PASTE(BUF_PREFIX, name)

/* ---- Create ---- */

#ifdef BUF_IS_FIXEDSTR
static BufHandle *BUF_FN(create)(const char *path, uint64_t capacity,
                                  uint32_t str_len, char *errbuf) {
    if (str_len == 0) {
        snprintf(errbuf, BUF_ERR_BUFLEN, "str_len must be > 0");
        return NULL;
    }
    return buf_create_map(path, capacity, str_len, BUF_VARIANT_ID, errbuf);
}
#else
static BufHandle *BUF_FN(create)(const char *path, uint64_t capacity, char *errbuf) {
    return buf_create_map(path, capacity, BUF_ELEM_SIZE, BUF_VARIANT_ID, errbuf);
}
#endif

/* ---- Create anonymous ---- */

#ifdef BUF_IS_FIXEDSTR
static BufHandle *BUF_FN(create_anon)(uint64_t capacity, uint32_t str_len, char *errbuf) {
    if (str_len == 0) { snprintf(errbuf, BUF_ERR_BUFLEN, "str_len must be > 0"); return NULL; }
    return buf_create_anon(capacity, str_len, BUF_VARIANT_ID, errbuf);
}
static BufHandle *BUF_FN(create_memfd)(const char *name, uint64_t capacity, uint32_t str_len, char *errbuf) {
    if (str_len == 0) { snprintf(errbuf, BUF_ERR_BUFLEN, "str_len must be > 0"); return NULL; }
    return buf_create_memfd(name, capacity, str_len, BUF_VARIANT_ID, errbuf);
}
static BufHandle *BUF_FN(open_fd)(int fd, uint32_t str_len, char *errbuf) {
    if (str_len == 0) { snprintf(errbuf, BUF_ERR_BUFLEN, "str_len must be > 0"); return NULL; }
    return buf_open_fd(fd, str_len, BUF_VARIANT_ID, errbuf);
}
#else
static BufHandle *BUF_FN(create_anon)(uint64_t capacity, char *errbuf) {
    return buf_create_anon(capacity, BUF_ELEM_SIZE, BUF_VARIANT_ID, errbuf);
}
static BufHandle *BUF_FN(create_memfd)(const char *name, uint64_t capacity, char *errbuf) {
    return buf_create_memfd(name, capacity, BUF_ELEM_SIZE, BUF_VARIANT_ID, errbuf);
}
static BufHandle *BUF_FN(open_fd)(int fd, char *errbuf) {
    return buf_open_fd(fd, BUF_ELEM_SIZE, BUF_VARIANT_ID, errbuf);
}
#endif

/* ---- Raw byte access (for packed binary interop) ---- */

static int BUF_FN(get_raw)(BufHandle *h, uint64_t byte_off, uint64_t nbytes, void *out) {
    uint64_t data_size = h->hdr->capacity * (uint64_t)h->hdr->elem_size;
    if (nbytes > data_size || byte_off > data_size - nbytes) return 0;
    char *data = (char *)h->data;
    if (h->wr_locked) {
        memcpy(out, data + byte_off, (size_t)nbytes);
    } else {
        uint32_t seq_start;
        do {
            seq_start = buf_seqlock_read_begin(h->hdr);
            memcpy(out, data + byte_off, (size_t)nbytes);
        } while (buf_seqlock_read_retry(&h->hdr->seq, seq_start));
    }
    return 1;
}

static int BUF_FN(set_raw)(BufHandle *h, uint64_t byte_off, uint64_t nbytes, const void *in) {
    uint64_t data_size = h->hdr->capacity * (uint64_t)h->hdr->elem_size;
    if (nbytes > data_size || byte_off > data_size - nbytes) return 0;
    char *data = (char *)h->data;
    int nested = h->wr_locked;
    if (!nested) { buf_rwlock_wrlock(h); buf_seqlock_write_begin(&h->hdr->seq); }
    memcpy(data + byte_off, in, (size_t)nbytes);
    if (!nested) { buf_seqlock_write_end(&h->hdr->seq); buf_rwlock_wrunlock(h); }
    return 1;
}

/* ---- Clear (zero entire buffer) ---- */

static void BUF_FN(clear)(BufHandle *h) {
    BufHeader *hdr = h->hdr;
    int nested = h->wr_locked;
    if (!nested) { buf_rwlock_wrlock(h); buf_seqlock_write_begin(&hdr->seq); }
    memset(h->data, 0, (size_t)(hdr->capacity * hdr->elem_size));
    if (!nested) { buf_seqlock_write_end(&hdr->seq); buf_rwlock_wrunlock(h); }
}

/* ---- Single-element atomic get (lock-free for numeric types) ---- */

#ifdef BUF_IS_FIXEDSTR

static int BUF_FN(get)(BufHandle *h, uint64_t idx, char *out, uint32_t *out_len) {
    BufHeader *hdr = h->hdr;
    uint32_t esz = hdr->elem_size;
    if (idx >= hdr->capacity) return 0;
    char *data = (char *)h->data;
    if (h->wr_locked) {
        memcpy(out, data + idx * esz, esz);
    } else {
        uint32_t seq_start;
        do {
            seq_start = buf_seqlock_read_begin(hdr);
            memcpy(out, data + idx * esz, esz);
        } while (buf_seqlock_read_retry(&hdr->seq, seq_start));
    }
    uint32_t len = esz;
    while (len > 0 && out[len - 1] == '\0') len--;
    *out_len = len;
    return 1;
}

static int BUF_FN(set)(BufHandle *h, uint64_t idx, const char *val, uint32_t len) {
    BufHeader *hdr = h->hdr;
    uint32_t esz = hdr->elem_size;
    if (idx >= hdr->capacity) return 0;
    char *data = (char *)h->data;
    int nested = h->wr_locked;
    if (!nested) { buf_rwlock_wrlock(h); buf_seqlock_write_begin(&hdr->seq); }
    memset(data + idx * esz, 0, esz);
    uint32_t copy_len = len < esz ? len : esz;
    memcpy(data + idx * esz, val, copy_len);
    if (!nested) { buf_seqlock_write_end(&hdr->seq); buf_rwlock_wrunlock(h); }
    return 1;
}

#elif defined(BUF_IS_FLOAT)

/* Float/double: GCC __atomic builtins don't support FP types.
 * Use same-sized integer atomic load/store + memcpy for lock-free access. */

#if BUF_ELEM_SIZE == 4
typedef uint32_t BUF_PASTE(BUF_PREFIX, _uint_t);
#elif BUF_ELEM_SIZE == 8
typedef uint64_t BUF_PASTE(BUF_PREFIX, _uint_t);
#else
#error "BUF_IS_FLOAT requires BUF_ELEM_SIZE of 4 or 8"
#endif

static int BUF_FN(get)(BufHandle *h, uint64_t idx, BUF_ELEM_TYPE *out) {
    BufHeader *hdr = h->hdr;
    if (idx >= hdr->capacity) return 0;
    typedef BUF_PASTE(BUF_PREFIX, _uint_t) uint_t;
    uint_t *idata = (uint_t *)h->data;
    uint_t tmp = __atomic_load_n(&idata[idx], __ATOMIC_RELAXED);
    memcpy(out, &tmp, sizeof(BUF_ELEM_TYPE));
    return 1;
}

static int BUF_FN(set)(BufHandle *h, uint64_t idx, BUF_ELEM_TYPE val) {
    BufHeader *hdr = h->hdr;
    if (idx >= hdr->capacity) return 0;
    typedef BUF_PASTE(BUF_PREFIX, _uint_t) uint_t;
    uint_t *idata = (uint_t *)h->data;
    uint_t tmp;
    memcpy(&tmp, &val, sizeof(BUF_ELEM_TYPE));
    __atomic_store_n(&idata[idx], tmp, __ATOMIC_RELAXED);
    return 1;
}

#else /* integer types */

static int BUF_FN(get)(BufHandle *h, uint64_t idx, BUF_ELEM_TYPE *out) {
    BufHeader *hdr = h->hdr;
    if (idx >= hdr->capacity) return 0;
    BUF_ELEM_TYPE *data = (BUF_ELEM_TYPE *)h->data;
    *out = __atomic_load_n(&data[idx], __ATOMIC_RELAXED);
    return 1;
}

static int BUF_FN(set)(BufHandle *h, uint64_t idx, BUF_ELEM_TYPE val) {
    BufHeader *hdr = h->hdr;
    if (idx >= hdr->capacity) return 0;
    BUF_ELEM_TYPE *data = (BUF_ELEM_TYPE *)h->data;
    __atomic_store_n(&data[idx], val, __ATOMIC_RELAXED);
    return 1;
}

#endif /* BUF_IS_FIXEDSTR */

/* ---- Bulk operations (seqlock-guarded) ---- */

#ifdef BUF_IS_FIXEDSTR

static int BUF_FN(get_slice)(BufHandle *h, uint64_t from, uint64_t count,
                              void *out) {
    BufHeader *hdr = h->hdr;
    uint32_t esz = hdr->elem_size;
    if (count > hdr->capacity || from > hdr->capacity - count) return 0;
    char *data = (char *)h->data;
    if (h->wr_locked) {
        memcpy(out, data + from * esz, count * esz);
    } else {
        uint32_t seq_start;
        do {
            seq_start = buf_seqlock_read_begin(hdr);
            memcpy(out, data + from * esz, count * esz);
        } while (buf_seqlock_read_retry(&hdr->seq, seq_start));
    }
    return 1;
}

static int BUF_FN(set_slice)(BufHandle *h, uint64_t from, uint64_t count,
                              const void *in) {
    BufHeader *hdr = h->hdr;
    uint32_t esz = hdr->elem_size;
    if (count > hdr->capacity || from > hdr->capacity - count) return 0;
    char *data = (char *)h->data;
    int nested = h->wr_locked;
    if (!nested) { buf_rwlock_wrlock(h); buf_seqlock_write_begin(&hdr->seq); }
    memcpy(data + from * esz, in, count * esz);
    if (!nested) { buf_seqlock_write_end(&hdr->seq); buf_rwlock_wrunlock(h); }
    return 1;
}

#else /* numeric */

static int BUF_FN(get_slice)(BufHandle *h, uint64_t from, uint64_t count,
                              BUF_ELEM_TYPE *out) {
    BufHeader *hdr = h->hdr;
    if (count > hdr->capacity || from > hdr->capacity - count) return 0;
    BUF_ELEM_TYPE *data = (BUF_ELEM_TYPE *)h->data;
    if (h->wr_locked) {
        memcpy(out, &data[from], count * sizeof(BUF_ELEM_TYPE));
    } else {
        uint32_t seq_start;
        do {
            seq_start = buf_seqlock_read_begin(hdr);
            memcpy(out, &data[from], count * sizeof(BUF_ELEM_TYPE));
        } while (buf_seqlock_read_retry(&hdr->seq, seq_start));
    }
    return 1;
}

static int BUF_FN(set_slice)(BufHandle *h, uint64_t from, uint64_t count,
                              const BUF_ELEM_TYPE *in) {
    BufHeader *hdr = h->hdr;
    if (count > hdr->capacity || from > hdr->capacity - count) return 0;
    BUF_ELEM_TYPE *data = (BUF_ELEM_TYPE *)h->data;
    int nested = h->wr_locked;
    if (!nested) { buf_rwlock_wrlock(h); buf_seqlock_write_begin(&hdr->seq); }
    memcpy(&data[from], in, count * sizeof(BUF_ELEM_TYPE));
    if (!nested) { buf_seqlock_write_end(&hdr->seq); buf_rwlock_wrunlock(h); }
    return 1;
}

#endif /* BUF_IS_FIXEDSTR */

/* ---- Fill ---- */

#ifdef BUF_IS_FIXEDSTR

static void BUF_FN(fill)(BufHandle *h, const char *val, uint32_t len) {
    BufHeader *hdr = h->hdr;
    uint32_t esz = hdr->elem_size;
    char *data = (char *)h->data;
    int nested = h->wr_locked;
    if (!nested) { buf_rwlock_wrlock(h); buf_seqlock_write_begin(&hdr->seq); }
    uint32_t copy_len = len < esz ? len : esz;
    memset(data, 0, (size_t)hdr->capacity * esz);
    for (uint64_t i = 0; i < hdr->capacity; i++)
        memcpy(data + i * esz, val, copy_len);
    if (!nested) { buf_seqlock_write_end(&hdr->seq); buf_rwlock_wrunlock(h); }
}

#else

static void BUF_FN(fill)(BufHandle *h, BUF_ELEM_TYPE val) {
    BufHeader *hdr = h->hdr;
    BUF_ELEM_TYPE *data = (BUF_ELEM_TYPE *)h->data;
    int nested = h->wr_locked;
    if (!nested) { buf_rwlock_wrlock(h); buf_seqlock_write_begin(&hdr->seq); }
    for (uint64_t i = 0; i < hdr->capacity; i++)
        data[i] = val;
    if (!nested) { buf_seqlock_write_end(&hdr->seq); buf_rwlock_wrunlock(h); }
}

#endif

/* ---- Atomic operations (integer types only) ---- */

#ifdef BUF_HAS_COUNTERS

static BUF_ELEM_TYPE BUF_FN(incr)(BufHandle *h, uint64_t idx) {
    if (idx >= h->hdr->capacity) return 0;
    BUF_ELEM_TYPE *data = (BUF_ELEM_TYPE *)h->data;
    return __atomic_add_fetch(&data[idx], 1, __ATOMIC_RELAXED);
}

static BUF_ELEM_TYPE BUF_FN(decr)(BufHandle *h, uint64_t idx) {
    if (idx >= h->hdr->capacity) return 0;
    BUF_ELEM_TYPE *data = (BUF_ELEM_TYPE *)h->data;
    return __atomic_sub_fetch(&data[idx], 1, __ATOMIC_RELAXED);
}

static BUF_ELEM_TYPE BUF_FN(add)(BufHandle *h, uint64_t idx, BUF_ELEM_TYPE delta) {
    if (idx >= h->hdr->capacity) return 0;
    BUF_ELEM_TYPE *data = (BUF_ELEM_TYPE *)h->data;
    return __atomic_add_fetch(&data[idx], delta, __ATOMIC_RELAXED);
}

static int BUF_FN(cas)(BufHandle *h, uint64_t idx,
                        BUF_ELEM_TYPE expected, BUF_ELEM_TYPE desired) {
    if (idx >= h->hdr->capacity) return 0;
    BUF_ELEM_TYPE *data = (BUF_ELEM_TYPE *)h->data;
    return __atomic_compare_exchange_n(&data[idx], &expected, desired,
                                        0, __ATOMIC_ACQ_REL, __ATOMIC_RELAXED);
}

static BUF_ELEM_TYPE BUF_FN(cmpxchg)(BufHandle *h, uint64_t idx,
                                       BUF_ELEM_TYPE expected, BUF_ELEM_TYPE desired) {
    if (idx >= h->hdr->capacity) return expected;
    BUF_ELEM_TYPE *data = (BUF_ELEM_TYPE *)h->data;
    __atomic_compare_exchange_n(&data[idx], &expected, desired,
                                0, __ATOMIC_ACQ_REL, __ATOMIC_RELAXED);
    return expected; /* on failure, expected is updated to the current value */
}

static BUF_ELEM_TYPE BUF_FN(atomic_and)(BufHandle *h, uint64_t idx, BUF_ELEM_TYPE mask) {
    if (idx >= h->hdr->capacity) return 0;
    BUF_ELEM_TYPE *data = (BUF_ELEM_TYPE *)h->data;
    return __atomic_and_fetch(&data[idx], mask, __ATOMIC_RELAXED);
}

static BUF_ELEM_TYPE BUF_FN(atomic_or)(BufHandle *h, uint64_t idx, BUF_ELEM_TYPE mask) {
    if (idx >= h->hdr->capacity) return 0;
    BUF_ELEM_TYPE *data = (BUF_ELEM_TYPE *)h->data;
    return __atomic_or_fetch(&data[idx], mask, __ATOMIC_RELAXED);
}

static BUF_ELEM_TYPE BUF_FN(atomic_xor)(BufHandle *h, uint64_t idx, BUF_ELEM_TYPE mask) {
    if (idx >= h->hdr->capacity) return 0;
    BUF_ELEM_TYPE *data = (BUF_ELEM_TYPE *)h->data;
    return __atomic_xor_fetch(&data[idx], mask, __ATOMIC_RELAXED);
}

static int BUF_FN(add_slice)(BufHandle *h, uint64_t from, uint64_t count,
                              const BUF_ELEM_TYPE *deltas) {
    if (count > h->hdr->capacity || from > h->hdr->capacity - count) return 0;
    BUF_ELEM_TYPE *data = (BUF_ELEM_TYPE *)h->data;
    for (uint64_t i = 0; i < count; i++)
        __atomic_add_fetch(&data[from + i], deltas[i], __ATOMIC_RELAXED);
    return 1;
}

#endif /* BUF_HAS_COUNTERS */

/* ---- Diagnostics ---- */

static inline uint64_t BUF_FN(capacity)(BufHandle *h) {
    return h->hdr->capacity;
}

static inline uint64_t BUF_FN(mmap_size)(BufHandle *h) {
    return (uint64_t)h->mmap_size;
}

static inline uint32_t BUF_FN(elem_size)(BufHandle *h) {
    return h->hdr->elem_size;
}

/* ---- Raw pointer access (for passing to external C/XS code) ---- */

static inline void *BUF_FN(ptr)(BufHandle *h) {
    return h->data;
}

static inline void *BUF_FN(ptr_at)(BufHandle *h, uint64_t idx) {
    if (idx >= h->hdr->capacity) return NULL;
    return (char *)h->data + idx * h->hdr->elem_size;
}

/* ---- Explicit locking for batch operations ---- */

static inline void BUF_FN(lock_wr)(BufHandle *h) {
    buf_rwlock_wrlock(h);
    buf_seqlock_write_begin(&h->hdr->seq);
    h->wr_locked = 1;
}

static inline void BUF_FN(unlock_wr)(BufHandle *h) {
    h->wr_locked = 0;
    buf_seqlock_write_end(&h->hdr->seq);
    buf_rwlock_wrunlock(h);
}

static inline void BUF_FN(lock_rd)(BufHandle *h) {
    buf_rwlock_rdlock(h);
}

static inline void BUF_FN(unlock_rd)(BufHandle *h) {
    buf_rwlock_rdunlock(h);
}

/* ---- Cleanup ---- */

#undef BUF_PASTE2
#undef BUF_PASTE
#undef BUF_FN
#undef BUF_PREFIX
#undef BUF_ELEM_TYPE
#undef BUF_ELEM_SIZE
#undef BUF_VARIANT_ID
#ifdef BUF_HAS_COUNTERS
#undef BUF_HAS_COUNTERS
#endif
#ifdef BUF_IS_FLOAT
#undef BUF_IS_FLOAT
#endif
#ifdef BUF_IS_FIXEDSTR
#undef BUF_IS_FIXEDSTR
#endif



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