calog/libs/calogHandle.c

// calogHandle.c -- thread-safe, typed integer handle table (see calogHandle.h).

#include "calogHandle.h"

#include <pthread.h>
#include <stdlib.h>

#define HANDLE_INITIAL_CAP 8
#define HANDLE_GROWTH      2

// A free slot has handle == 0; the monotonic nextHandle starts at 1, so 0 is never a
// live handle and doubles as the "invalid" sentinel a caller can test.
typedef struct HandleEntryT {
    int64_t  handle;
    uint32_t type;
    void    *resource;
} HandleEntryT;

struct CalogHandleTableT {
    pthread_mutex_t mutex;
    HandleEntryT   *entries;
    int32_t         count;
    int32_t         cap;
    int64_t         nextHandle;
};


int64_t calogHandleAdd(CalogHandleTableT *table, uint32_t type, void *resource) {
    int64_t handle;
    int32_t slot;
    int32_t index;

    pthread_mutex_lock(&table->mutex);
    slot = -1;
    for (index = 0; index < table->count; index++) {
        if (table->entries[index].handle == 0) {
            slot = index;
            break;
        }
    }
    if (slot < 0) {
        if (table->count == table->cap) {
            int32_t       newCap;
            HandleEntryT *grown;
            newCap = (table->cap == 0) ? HANDLE_INITIAL_CAP : table->cap * HANDLE_GROWTH;
            grown  = (HandleEntryT *)realloc(table->entries, (size_t)newCap * sizeof(HandleEntryT));
            if (grown == NULL) {
                pthread_mutex_unlock(&table->mutex);
                return 0;
            }
            table->entries = grown;
            table->cap     = newCap;
        }
        slot = table->count;
        table->count++;
    }
    handle = table->nextHandle;
    table->nextHandle++;
    table->entries[slot].handle   = handle;
    table->entries[slot].type     = type;
    table->entries[slot].resource = resource;
    pthread_mutex_unlock(&table->mutex);
    return handle;
}


int32_t calogHandleCount(CalogHandleTableT *table, uint32_t type) {
    int32_t count;
    int32_t index;

    count = 0;
    pthread_mutex_lock(&table->mutex);
    for (index = 0; index < table->count; index++) {
        if (table->entries[index].handle != 0 && table->entries[index].type == type) {
            count++;
        }
    }
    pthread_mutex_unlock(&table->mutex);
    return count;
}


void *calogHandleGet(CalogHandleTableT *table, int64_t handle, uint32_t type) {
    void   *resource;
    int32_t index;

    // Valid handles are >= 1; reject 0 (the free-slot sentinel) and negatives so a bogus or
    // zero handle can never alias a freed slot.
    if (handle <= 0) {
        return NULL;
    }
    resource = NULL;
    pthread_mutex_lock(&table->mutex);
    for (index = 0; index < table->count; index++) {
        if (table->entries[index].handle == handle && table->entries[index].type == type) {
            resource = table->entries[index].resource;
            break;
        }
    }
    pthread_mutex_unlock(&table->mutex);
    return resource;
}


void *calogHandleRemove(CalogHandleTableT *table, int64_t handle, uint32_t type) {
    void   *resource;
    int32_t index;

    if (handle <= 0) {
        return NULL;
    }
    resource = NULL;
    pthread_mutex_lock(&table->mutex);
    for (index = 0; index < table->count; index++) {
        if (table->entries[index].handle == handle && table->entries[index].type == type) {
            resource                       = table->entries[index].resource;
            table->entries[index].handle   = 0;
            table->entries[index].type     = 0;
            table->entries[index].resource = NULL;
            break;
        }
    }
    pthread_mutex_unlock(&table->mutex);
    return resource;
}


CalogHandleTableT *calogHandleTableCreate(void) {
    CalogHandleTableT *table;

    table = (CalogHandleTableT *)calloc(1, sizeof(*table));
    if (table == NULL) {
        return NULL;
    }
    pthread_mutex_init(&table->mutex, NULL);
    table->nextHandle = 1;
    return table;
}


void calogHandleTableDestroy(CalogHandleTableT *table, CalogHandleCloserT closer) {
    int32_t index;

    if (table == NULL) {
        return;
    }
    for (index = 0; index < table->count; index++) {
        if (table->entries[index].handle != 0 && closer != NULL) {
            closer(table->entries[index].type, table->entries[index].resource);
        }
    }
    free(table->entries);
    pthread_mutex_destroy(&table->mutex);
    free(table);
}