/*
 * name-hash.c
 *
 * Hashing names in the index state
 *
 * Copyright (C) 2008 Linus Torvalds
 */
#define NO_THE_INDEX_COMPATIBILITY_MACROS
#include "cache.h"

/*
 * This removes bit 5 if bit 6 is set.
 *
 * That will make US-ASCII characters hash to their upper-case
 * equivalent. We could easily do this one whole word at a time,
 * but that's for future worries.
 */
static inline unsigned char icase_hash(unsigned char c)
{
        return c & ~((c & 0x40) >> 1);
}

static unsigned int hash_name(const char *name, int namelen)
{
        unsigned int hash = 0x123;

        while (namelen--) {
                unsigned char c = *name++;
                c = icase_hash(c);
                hash = hash*101 + c;
        }
        return hash;
}

static void hash_index_entry_directories(struct index_state *istate, struct cache_entry *ce)
{
        /*
         * Throw each directory component in the hash for quick lookup
         * during a git status. Directory components are stored with their
         * closing slash.  Despite submodules being a directory, they never
         * reach this point, because they are stored without a closing slash
         * in the cache.
         *
         * Note that the cache_entry stored with the directory does not
         * represent the directory itself.  It is a pointer to an existing
         * filename, and its only purpose is to represent existence of the
         * directory in the cache.  It is very possible multiple directory
         * hash entries may point to the same cache_entry.
         */
        unsigned int hash;
        void **pos;

        const char *ptr = ce->name;
        while (*ptr) {
                while (*ptr && *ptr != '/')
                        ++ptr;
                if (*ptr == '/') {
                        ++ptr;
                        hash = hash_name(ce->name, ptr - ce->name);
                        pos = insert_hash(hash, ce, &istate->name_hash);
                        if (pos) {
                                ce->dir_next = *pos;
                                *pos = ce;
                        }
                }
        }
}

static void hash_index_entry(struct index_state *istate, struct cache_entry *ce)
{
        void **pos;
        unsigned int hash;

        if (ce->ce_flags & CE_HASHED)
                return;
        ce->ce_flags |= CE_HASHED;
        ce->next = ce->dir_next = NULL;
        hash = hash_name(ce->name, ce_namelen(ce));
        pos = insert_hash(hash, ce, &istate->name_hash);
        if (pos) {
                ce->next = *pos;
                *pos = ce;
        }

        if (ignore_case)
                hash_index_entry_directories(istate, ce);
}

static void lazy_init_name_hash(struct index_state *istate)
{
        int nr;

        if (istate->name_hash_initialized)
                return;
        if (istate->cache_nr)
                preallocate_hash(&istate->name_hash, istate->cache_nr);
        for (nr = 0; nr < istate->cache_nr; nr++)
                hash_index_entry(istate, istate->cache[nr]);
        istate->name_hash_initialized = 1;
}

void add_name_hash(struct index_state *istate, struct cache_entry *ce)
{
        ce->ce_flags &= ~CE_UNHASHED;
        if (istate->name_hash_initialized)
                hash_index_entry(istate, ce);
}

static int slow_same_name(const char *name1, int len1, const char *name2, int len2)
{
        if (len1 != len2)
                return 0;

        while (len1) {
                unsigned char c1 = *name1++;
                unsigned char c2 = *name2++;
                len1--;
                if (c1 != c2) {
                        c1 = toupper(c1);
                        c2 = toupper(c2);
                        if (c1 != c2)
                                return 0;
                }
        }
        return 1;
}

static int same_name(const struct cache_entry *ce, const char *name, int namelen, int icase)
{
        int len = ce_namelen(ce);

        /*
         * Always do exact compare, even if we want a case-ignoring comparison;
         * we do the quick exact one first, because it will be the common case.
         */
        if (len == namelen && !cache_name_compare(name, namelen, ce->name, len))
                return 1;

        if (!icase)
                return 0;

        /*
         * If the entry we're comparing is a filename (no trailing slash), then compare
         * the lengths exactly.
         */
        if (name[namelen - 1] != '/')
                return slow_same_name(name, namelen, ce->name, len);

        /*
         * For a directory, we point to an arbitrary cache_entry filename.  Just
         * make sure the directory portion matches.
         */
        return slow_same_name(name, namelen, ce->name, namelen < len ? namelen : len);
}

struct cache_entry *index_name_exists(struct index_state *istate, const char *name, int namelen, int icase)
{
        unsigned int hash = hash_name(name, namelen);
        struct cache_entry *ce;

        lazy_init_name_hash(istate);
        ce = lookup_hash(hash, &istate->name_hash);

        while (ce) {
                if (!(ce->ce_flags & CE_UNHASHED)) {
                        if (same_name(ce, name, namelen, icase))
                                return ce;
                }
                if (icase && name[namelen - 1] == '/')
                        ce = ce->dir_next;
                else
                        ce = ce->next;
        }

        /*
         * Might be a submodule.  Despite submodules being directories,
         * they are stored in the name hash without a closing slash.
         * When ignore_case is 1, directories are stored in the name hash
         * with their closing slash.
         *
         * The side effect of this storage technique is we have need to
         * remove the slash from name and perform the lookup again without
         * the slash.  If a match is made, S_ISGITLINK(ce->mode) will be
         * true.
         */
        if (icase && name[namelen - 1] == '/') {
                ce = index_name_exists(istate, name, namelen - 1, icase);
                if (ce && S_ISGITLINK(ce->ce_mode))
                        return ce;
        }
        return NULL;
}