From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-4.2 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id 13EDD1F461 for ; Mon, 13 May 2019 17:28:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731729AbfEMR2D (ORCPT ); Mon, 13 May 2019 13:28:03 -0400 Received: from mail-ed1-f42.google.com ([209.85.208.42]:36051 "EHLO mail-ed1-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731719AbfEMR2C (ORCPT ); Mon, 13 May 2019 13:28:02 -0400 Received: by mail-ed1-f42.google.com with SMTP id a8so18692377edx.3 for ; Mon, 13 May 2019 10:28:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:message-id:in-reply-to:references:from:subject:fcc :content-transfer-encoding:mime-version:to:cc; bh=ixYXw8fT/8FZkxOeJ2DHrv5O1KDRx4t4Dnxjc2qMUc8=; b=hrgf6blpVprU50PwFGdacadDKMkdV1V/ne5TxLzoP/gfyQWONTpwsb6yqLegGV+EdB g4Y6R1dmfYuyVAOy7HYZYdqIDHZREMWoFVnAKtI7RP2T/Tu6HstYm6da0Yttj//2hxUL Lvb/76BvfCKsq7rodwQl1H5CC8D2TtxJ66jISVuOofjBEmoW/3jHceBi0+zdGYdm7Wy0 z7YIiMEsOuh/yk9iSOmXl4KaTZNKj7qFaQVsqscZKjlo4N6/947vkQetEcs72MjMUhIF jPG2e/DA/GwJbL8bvFHZywNN23xR/e1pPPXh7h0sFoBCjYy9WZF1cSy/dwlR7yCYiO7d wq1Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:in-reply-to:references:from :subject:fcc:content-transfer-encoding:mime-version:to:cc; bh=ixYXw8fT/8FZkxOeJ2DHrv5O1KDRx4t4Dnxjc2qMUc8=; b=lu4kr7Wj3P/ZG7QATeuE9CR5ne0s/ERu3fej+usbTK0i322SYq5GPuQDeQYlmkbQp7 eH0yYDP7Prpv2iH0FFP/1nqjODQLV1SBB138XUwm70vtepymLkTzu8nbRsVekosH5q6D Eqc9e7NcyasBFi8m89pbiOYN6H8JjZXfYyuADLnvvXgKkBgArb4Q6zhvSs/QqDL/ENy/ D/4qYo5Y9g64595ta7ofdOy6eCUG8gbg3gzQeLu5rdixxrWiUjvABn93ZF/gkvu7x+ER eRZKxWQoHzrGdDjnW3bATfFELTpTBaV/PvWBVZDHv9Bl6y58PkWn46rJEMI1SpzzrZSL 3Wsg== X-Gm-Message-State: APjAAAVAohMt7Cze44cv9q/XWFN7vZD5vrhDbcUFzSPSrN4aOnsCAvfC FFqWq8p2wZx0OCKdFMSBqhkIXjgX X-Google-Smtp-Source: APXvYqy2yDXauI4LBua+Aoq6IGjzAEb2tNuDafvD4vwOlkWM7Q0mJUD+9VddeTStGGgJSiTh9JPFmw== X-Received: by 2002:a17:906:ef1:: with SMTP id x17mr23435838eji.15.1557768479376; Mon, 13 May 2019 10:27:59 -0700 (PDT) Received: from [127.0.0.1] ([13.74.141.28]) by smtp.gmail.com with ESMTPSA id c49sm3916366eda.58.2019.05.13.10.27.58 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 13 May 2019 10:27:58 -0700 (PDT) Date: Mon, 13 May 2019 10:27:58 -0700 (PDT) X-Google-Original-Date: Mon, 13 May 2019 17:27:47 GMT Message-Id: In-Reply-To: References: From: "Slavica Djukic via GitGitGadget" Subject: [PATCH v2 07/11] Add a function to determine unique prefixes for a list of strings Fcc: Sent Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit MIME-Version: 1.0 To: git@vger.kernel.org Cc: Jeff Hostetler , Jeff King , Junio C Hamano , Slavica Djukic Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org From: Slavica Djukic In the `git add -i` command, we show unique prefixes of the commands and files, to give an indication what prefix would select them. Naturally, the C implementation looks a lot different than the Perl implementation: in Perl, a trie is much easier implemented, while we already have a pretty neat hashmap implementation in C that we use for the purpose of storing (not necessarily unique) prefixes. The idea: for each item that we add, we generate prefixes starting with the first letter, then the first two letters, then three, etc, until we find a prefix that is unique (or until the prefix length would be longer than we want). If we encounter a previously-unique prefix on the way, we adjust that item's prefix to make it unique again (or we mark it as having no unique prefix if we failed to find one). These partial prefixes are stored in a hash map (for quick lookup times). To make sure that this function works as expected, we add a test using a special-purpose test helper that was added for that purpose. Note: We expect the list of prefix items to be passed in as a list of pointers rather than as regular list to avoid having to copy information (the actual items will most likely contain more information than just the name and the length of the unique prefix, but passing in `struct prefix_item *` would not allow for that). Signed-off-by: Slavica Djukic Signed-off-by: Johannes Schindelin --- Makefile | 2 + prefix-map.c | 109 +++++++++++++++++++++++++++++++++++++ prefix-map.h | 40 ++++++++++++++ t/helper/test-prefix-map.c | 58 ++++++++++++++++++++ t/helper/test-tool.c | 1 + t/helper/test-tool.h | 1 + t/t0016-prefix-map.sh | 10 ++++ 7 files changed, 221 insertions(+) create mode 100644 prefix-map.c create mode 100644 prefix-map.h create mode 100644 t/helper/test-prefix-map.c create mode 100755 t/t0016-prefix-map.sh diff --git a/Makefile b/Makefile index 18e656a32f..8299b3f17d 100644 --- a/Makefile +++ b/Makefile @@ -754,6 +754,7 @@ TEST_BUILTINS_OBJS += test-online-cpus.o TEST_BUILTINS_OBJS += test-parse-options.o TEST_BUILTINS_OBJS += test-path-utils.o TEST_BUILTINS_OBJS += test-pkt-line.o +TEST_BUILTINS_OBJS += test-prefix-map.o TEST_BUILTINS_OBJS += test-prio-queue.o TEST_BUILTINS_OBJS += test-reach.o TEST_BUILTINS_OBJS += test-read-cache.o @@ -967,6 +968,7 @@ LIB_OBJS += patch-ids.o LIB_OBJS += path.o LIB_OBJS += pathspec.o LIB_OBJS += pkt-line.o +LIB_OBJS += prefix-map.o LIB_OBJS += preload-index.o LIB_OBJS += pretty.o LIB_OBJS += prio-queue.o diff --git a/prefix-map.c b/prefix-map.c new file mode 100644 index 0000000000..747ddb4ebc --- /dev/null +++ b/prefix-map.c @@ -0,0 +1,109 @@ +#include "cache.h" +#include "prefix-map.h" + +static int map_cmp(const void *unused_cmp_data, + const void *entry, + const void *entry_or_key, + const void *unused_keydata) +{ + const struct prefix_map_entry *a = entry; + const struct prefix_map_entry *b = entry_or_key; + + return a->prefix_length != b->prefix_length || + strncmp(a->name, b->name, a->prefix_length); +} + +static void add_prefix_entry(struct hashmap *map, const char *name, + size_t prefix_length, struct prefix_item *item) +{ + struct prefix_map_entry *result = xmalloc(sizeof(*result)); + result->name = name; + result->prefix_length = prefix_length; + result->item = item; + hashmap_entry_init(result, memhash(name, prefix_length)); + hashmap_add(map, result); +} + +static void init_prefix_map(struct prefix_map *prefix_map, + int min_prefix_length, int max_prefix_length) +{ + hashmap_init(&prefix_map->map, map_cmp, NULL, 0); + prefix_map->min_length = min_prefix_length; + prefix_map->max_length = max_prefix_length; +} + +static void add_prefix_item(struct prefix_map *prefix_map, + struct prefix_item *item) +{ + struct prefix_map_entry e = { { NULL } }, *e2; + int j; + + e.item = item; + e.name = item->name; + + for (j = prefix_map->min_length; + j <= prefix_map->max_length && e.name[j]; j++) { + /* Avoid breaking UTF-8 multi-byte sequences */ + if (!isascii(e.name[j])) + break; + + e.prefix_length = j; + hashmap_entry_init(&e, memhash(e.name, j)); + e2 = hashmap_get(&prefix_map->map, &e, NULL); + if (!e2) { + /* prefix is unique at this stage */ + item->prefix_length = j; + add_prefix_entry(&prefix_map->map, e.name, j, item); + break; + } + + if (!e2->item) + continue; /* non-unique prefix */ + + if (j != e2->item->prefix_length || memcmp(e.name, e2->name, j)) + BUG("unexpected prefix length: %d != %d (%s != %s)", + j, (int)e2->item->prefix_length, e.name, e2->name); + + /* skip common prefix */ + for (; j < prefix_map->max_length && e.name[j]; j++) { + if (e.item->name[j] != e2->item->name[j]) + break; + add_prefix_entry(&prefix_map->map, e.name, j + 1, + NULL); + } + + /* e2 no longer refers to a unique prefix */ + if (j < prefix_map->max_length && e2->name[j]) { + /* found a new unique prefix for e2's item */ + e2->item->prefix_length = j + 1; + add_prefix_entry(&prefix_map->map, e2->name, j + 1, + e2->item); + } + else + e2->item->prefix_length = 0; + e2->item = NULL; + + if (j < prefix_map->max_length && e.name[j]) { + /* found a unique prefix for the item */ + e.item->prefix_length = j + 1; + add_prefix_entry(&prefix_map->map, e.name, j + 1, + e.item); + } else + /* item has no (short enough) unique prefix */ + e.item->prefix_length = 0; + + break; + } +} + +void find_unique_prefixes(struct prefix_item **list, size_t nr, + int min_length, int max_length) +{ + int i; + struct prefix_map prefix_map; + + init_prefix_map(&prefix_map, min_length, max_length); + for (i = 0; i < nr; i++) + add_prefix_item(&prefix_map, list[i]); + hashmap_free(&prefix_map.map, 1); +} diff --git a/prefix-map.h b/prefix-map.h new file mode 100644 index 0000000000..ce3b8a4a32 --- /dev/null +++ b/prefix-map.h @@ -0,0 +1,40 @@ +#ifndef PREFIX_MAP_H +#define PREFIX_MAP_H + +#include "hashmap.h" + +struct prefix_item { + const char *name; + size_t prefix_length; +}; + +struct prefix_map_entry { + struct hashmap_entry e; + const char *name; + size_t prefix_length; + /* if item is NULL, the prefix is not unique */ + struct prefix_item *item; +}; + +struct prefix_map { + struct hashmap map; + int min_length, max_length; +}; + +/* + * Find unique prefixes in a given list of strings. + * + * Typically, the `struct prefix_item` information will be but a field in the + * actual item struct; For this reason, the `list` parameter is specified as a + * list of pointers to the items. + * + * The `min_length`/`max_length` parameters define what length the unique + * prefixes should have. + * + * If no unique prefix could be found for a given item, its `prefix_length` + * will be set to 0. + */ +void find_unique_prefixes(struct prefix_item **list, size_t nr, + int min_length, int max_length); + +#endif diff --git a/t/helper/test-prefix-map.c b/t/helper/test-prefix-map.c new file mode 100644 index 0000000000..3f1c90eaf0 --- /dev/null +++ b/t/helper/test-prefix-map.c @@ -0,0 +1,58 @@ +#include "test-tool.h" +#include "cache.h" +#include "prefix-map.h" + +static size_t test_count, failed_count; + +static void check(int succeeded, const char *file, size_t line_no, + const char *fmt, ...) +{ + va_list ap; + + test_count++; + if (succeeded) + return; + + va_start(ap, fmt); + fprintf(stderr, "%s:%d: ", file, (int)line_no); + vfprintf(stderr, fmt, ap); + fputc('\n', stderr); + va_end(ap); + + failed_count++; +} + +#define EXPECT_SIZE_T_EQUALS(expect, actual, hint) \ + check(expect == actual, __FILE__, __LINE__, \ + "size_t's do not match: %" \ + PRIdMAX " != %" PRIdMAX " (%s) (%s)", \ + (intmax_t)expect, (intmax_t)actual, #actual, hint) + +int cmd__prefix_map(int argc, const char **argv) +{ +#define NR 5 + struct prefix_item items[NR] = { + { "unique" }, + { "hell" }, + { "hello" }, + { "wok" }, + { "world" }, + }; + struct prefix_item *list[NR] = { + items, items + 1, items + 2, items + 3, items + 4 + }; + + find_unique_prefixes(list, NR, 1, 3); + +#define EXPECT_PREFIX_LENGTH_EQUALS(expect, index) \ + EXPECT_SIZE_T_EQUALS(expect, list[index]->prefix_length, \ + list[index]->name) + + EXPECT_PREFIX_LENGTH_EQUALS(1, 0); + EXPECT_PREFIX_LENGTH_EQUALS(0, 1); + EXPECT_PREFIX_LENGTH_EQUALS(0, 2); + EXPECT_PREFIX_LENGTH_EQUALS(3, 3); + EXPECT_PREFIX_LENGTH_EQUALS(3, 4); + + return !!failed_count; +} diff --git a/t/helper/test-tool.c b/t/helper/test-tool.c index 99db7409b8..d6a92a8699 100644 --- a/t/helper/test-tool.c +++ b/t/helper/test-tool.c @@ -32,6 +32,7 @@ static struct test_cmd cmds[] = { { "parse-options", cmd__parse_options }, { "path-utils", cmd__path_utils }, { "pkt-line", cmd__pkt_line }, + { "prefix-map", cmd__prefix_map }, { "prio-queue", cmd__prio_queue }, { "reach", cmd__reach }, { "read-cache", cmd__read_cache }, diff --git a/t/helper/test-tool.h b/t/helper/test-tool.h index 25abed1cf2..33a089ee4e 100644 --- a/t/helper/test-tool.h +++ b/t/helper/test-tool.h @@ -29,6 +29,7 @@ int cmd__online_cpus(int argc, const char **argv); int cmd__parse_options(int argc, const char **argv); int cmd__path_utils(int argc, const char **argv); int cmd__pkt_line(int argc, const char **argv); +int cmd__prefix_map(int argc, const char **argv); int cmd__prio_queue(int argc, const char **argv); int cmd__reach(int argc, const char **argv); int cmd__read_cache(int argc, const char **argv); diff --git a/t/t0016-prefix-map.sh b/t/t0016-prefix-map.sh new file mode 100755 index 0000000000..187fa92aec --- /dev/null +++ b/t/t0016-prefix-map.sh @@ -0,0 +1,10 @@ +#!/bin/sh + +test_description='basic tests for prefix map' +. ./test-lib.sh + +test_expect_success 'prefix map' ' + test-tool prefix-map +' + +test_done -- gitgitgadget