root/pack-objects.c

DEFINITIONS

1. locate_object_entry_hash
2. closest_pow2
3. rehash_objects
4. packlist_find
5. packlist_alloc

#include "cache.h"
#include "object.h"
#include "pack.h"
#include "pack-objects.h"

static uint32_t locate_object_entry_hash(struct packing_data *pdata,
                                         const unsigned char *sha1,
                                         int *found)
{
        uint32_t i, mask = (pdata->index_size - 1);

        i = sha1hash(sha1) & mask;

        while (pdata->index[i] > 0) {
                uint32_t pos = pdata->index[i] - 1;

                if (!hashcmp(sha1, pdata->objects[pos].idx.sha1)) {
                        *found = 1;
                        return i;
                }

                i = (i + 1) & mask;
        }

        *found = 0;
        return i;
}

static inline uint32_t closest_pow2(uint32_t v)
{
        v = v - 1;
        v |= v >> 1;
        v |= v >> 2;
        v |= v >> 4;
        v |= v >> 8;
        v |= v >> 16;
        return v + 1;
}

static void rehash_objects(struct packing_data *pdata)
{
        uint32_t i;
        struct object_entry *entry;

        pdata->index_size = closest_pow2(pdata->nr_objects * 3);
        if (pdata->index_size < 1024)
                pdata->index_size = 1024;

        free(pdata->index);
        pdata->index = xcalloc(pdata->index_size, sizeof(*pdata->index));

        entry = pdata->objects;

        for (i = 0; i < pdata->nr_objects; i++) {
                int found;
                uint32_t ix = locate_object_entry_hash(pdata, entry->idx.sha1, &found);

                if (found)
                        die("BUG: Duplicate object in hash");

                pdata->index[ix] = i + 1;
                entry++;
        }
}

struct object_entry *packlist_find(struct packing_data *pdata,
                                   const unsigned char *sha1,
                                   uint32_t *index_pos)
{
        uint32_t i;
        int found;

        if (!pdata->index_size)
                return NULL;

        i = locate_object_entry_hash(pdata, sha1, &found);

        if (index_pos)
                *index_pos = i;

        if (!found)
                return NULL;

        return &pdata->objects[pdata->index[i] - 1];
}

struct object_entry *packlist_alloc(struct packing_data *pdata,
                                    const unsigned char *sha1,
                                    uint32_t index_pos)
{
        struct object_entry *new_entry;

        if (pdata->nr_objects >= pdata->nr_alloc) {
                pdata->nr_alloc = (pdata->nr_alloc  + 1024) * 3 / 2;
                REALLOC_ARRAY(pdata->objects, pdata->nr_alloc);
        }

        new_entry = pdata->objects + pdata->nr_objects++;

        memset(new_entry, 0, sizeof(*new_entry));
        hashcpy(new_entry->idx.sha1, sha1);

        if (pdata->index_size * 3 <= pdata->nr_objects * 4)
                rehash_objects(pdata);
        else
                pdata->index[index_pos] = pdata->nr_objects;

        return new_entry;
}