{"id":20040763,"url":"https://github.com/vadimkantorov/libarchivedd","last_synced_at":"2025-03-02T06:46:49.614Z","repository":{"id":255340905,"uuid":"849285500","full_name":"vadimkantorov/libarchivedd","owner":"vadimkantorov","description":"libarchive primer of printing byte offsets/sizes for uncompressed entries in formats: TAR, ISO, ZIP","archived":false,"fork":false,"pushed_at":"2024-08-29T17:10:22.000Z","size":15,"stargazers_count":0,"open_issues_count":0,"forks_count":0,"subscribers_count":1,"default_branch":"master","last_synced_at":"2025-01-12T19:21:02.970Z","etag":null,"topics":["dd","file-systems","iso","libarchive","tar","zip"],"latest_commit_sha":null,"homepage":"","language":"C","has_issues":true,"has_wiki":null,"has_pages":null,"mirror_url":null,"source_name":null,"license":null,"status":null,"scm":"git","pull_requests_enabled":true,"icon_url":"https://github.com/vadimkantorov.png","metadata":{"files":{"readme":"README.md","changelog":null,"contributing":null,"funding":null,"license":null,"code_of_conduct":null,"threat_model":null,"audit":null,"citation":null,"codeowners":null,"security":null,"support":null,"governance":null,"roadmap":null,"authors":null,"dei":null,"publiccode":null,"codemeta":null}},"created_at":"2024-08-29T10:17:59.000Z","updated_at":"2024-08-29T17:10:25.000Z","dependencies_parsed_at":"2024-08-29T11:53:31.834Z","dependency_job_id":"e7f01bf1-a6c2-42cf-a7ad-802840eb8526","html_url":"https://github.com/vadimkantorov/libarchivedd","commit_stats":null,"previous_names":["vadimkantorov/libarchivedd"],"tags_count":0,"template":false,"template_full_name":null,"repository_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/vadimkantorov%2Flibarchivedd","tags_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/vadimkantorov%2Flibarchivedd/tags","releases_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/vadimkantorov%2Flibarchivedd/releases","manifests_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/vadimkantorov%2Flibarchivedd/manifests","owner_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners/vadimkantorov","download_url":"https://codeload.github.com/vadimkantorov/libarchivedd/tar.gz/refs/heads/master","host":{"name":"GitHub","url":"https://github.com","kind":"github","repositories_count":241470363,"owners_count":19968041,"icon_url":"https://github.com/github.png","version":null,"created_at":"2022-05-30T11:31:42.601Z","updated_at":"2022-07-04T15:15:14.044Z","host_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub","repositories_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories","repository_names_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repository_names","owners_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners"}},"keywords":["dd","file-systems","iso","libarchive","tar","zip"],"created_at":"2024-11-13T10:43:42.534Z","updated_at":"2025-03-02T06:46:49.555Z","avatar_url":"https://github.com/vadimkantorov.png","language":"C","funding_links":[],"categories":[],"sub_categories":[],"readme":"# [libarchive](https://github.com/libarchive/libarchive) primer of printing byte offsets/sizes for uncompressed entries in formats: TAR, ZIP, ISO\n\nOn 29 august 2024 [libarchive](https://github.com/libarchive/libarchive) does not support built-in calculation of byte offsets of uncompressed entries. So a hack is needed. This feature might hopefully be added natively to libarchive in the future (so the hack in this primer would become not needed), see [issues](https://github.com/libarchive/libarchive/issues/2295) referenced below. Hack was developed with help of `libarchive` maintainer in discussion in https://github.com/libarchive/libarchive/issues/2283\n\n[`libarhivedd.c`](./libarchivedd.c) is modeled after https://github.com/libarchive/libarchive/blob/master/examples/untar.c and https://github.com/libarchive/libarchive/wiki/Examples#A_Complete_Extractor, another useful example is https://github.com/libarchive/libarchive/blob/master/contrib/untar.c\n\n```shell\n# configures and build libarchive static lib and ./libarchivedd executable\nmake\n\n# prepare test archives\n# sudo apt install -y zip mkisofs\nmake libarchivedd.tar libarchivedd.zip libarchivedd.iso\n\n./libarchivedd libarchivedd.tar\n#dd if=\"libarchivedd.tar\" of=\"libarchivedd.c\" bs=1 skip=512 count=3756\n#dd if=\"libarchivedd.tar\" of=\"Makefile\" bs=1 skip=5120 count=616\n\n./libarchivedd libarchivedd.zip\n#dd if=\"libarchivedd.zip\" of=\"libarchivedd.c\" bs=1 skip=72 count=3756\n#dd if=\"libarchivedd.zip\" of=\"Makefile\" bs=1 skip=3894 count=616\n\n./libarchivedd libarchivedd.iso\n#false #. AE_IFDIR : 16384\n#dd if=\"libarchivedd.iso\" of=\"libarchivedd.c\" bs=1 skip=63488 count=3756\n#dd if=\"libarchivedd.iso\" of=\"Makefile\" bs=1 skip=67584 count=616\n```\n\n# References\n- https://github.com/libarchive/libarchive/issues/2295\n- https://github.com/libarchive/libarchive/issues/2283\n\n## Bonus: helpers of extracting an entry to fd, `FILE*` and mem buffer\n\n```cpp\nsize_t extract_to_fd(struct archive* a, const void* firstblock_buff, size_t firstblock_size, int64_t firstblock_offset, int fd)\n{\n    (void)firstblock_offset;\n    size_t size = write(fd, firstblock_buff, firstblock_size);\n    for(;;)\n    {\n        int r = archive_read_data_block(a, \u0026firstblock_buff, \u0026firstblock_size, \u0026firstblock_offset);\n        if (r == ARCHIVE_EOF || r != ARCHIVE_OK)\n\t    break;\n        assert(r == ARCHIVE_OK);\n        size += write(fd, firstblock_buff, firstblock_size);\n    }\n    return size;\n}\n\nsize_t extract_to_file(struct archive* a, const void* firstblock_buff, size_t firstblock_size, int64_t firstblock_offset, FILE* stream)\n{\n    (void)firstblock_offset;\n    size_t size = fwrite(firstblock_buff, 1, firstblock_size, stream);\n    for(;;)\n    {\n        int r = archive_read_data_block(a, \u0026firstblock_buff, \u0026firstblock_size, \u0026firstblock_offset);\n        if (r == ARCHIVE_EOF || r != ARCHIVE_OK)\n\t    break;\n        assert(r == ARCHIVE_OK);\n        size += fwrite(firstblock_buff, 1, firstblock_size, stream);\n    }\n    return size;\n}\n\nsize_t extract_to_mem(struct archive* a, const void* firstblock_buff, size_t firstblock_size, int64_t firstblock_offset, void* buf, size_t cnt)\n{\n    (void)firstblock_offset;\n    size_t size = firstblock_size \u003c= cnt ? firstblock_size : cnt;\n    memcpy(buf, firstblock_buff, size);\n    cnt -= size;\n    for(;;)\n    {\n        int r = archive_read_data_block(a, \u0026firstblock_buff, \u0026firstblock_size, \u0026firstblock_offset);\n        if (r == ARCHIVE_EOF || r != ARCHIVE_OK)\n\t    break;\n        assert(r == ARCHIVE_OK);\n        size_t w = firstblock_size \u003c= cnt ? firstblock_size : cnt;\n        memcpy((char*)buf + size, firstblock_buff, w);\n        cnt -= w;\n    }\n    return size;\n}\n\n// ... \n\n//extract_to_fd(a, firstblock_buff, firstblock_len, firstblock_offset, 2);\n//extract_to_file(a, firstblock_buff, firstblock_len, firstblock_offset, stderr);\n//char tmp[1024]; size_t size = extract_to_mem(a, firstblock_buff, firstblock_len, firstblock_offset, tmp, 1024); tmp[size \u003c= 1023 ? size : 1023] = '\\0'; fprintf(stderr, \"%s\", tmp);\n```\n","project_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fvadimkantorov%2Flibarchivedd","html_url":"https://awesome.ecosyste.ms/projects/github.com%2Fvadimkantorov%2Flibarchivedd","lists_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fvadimkantorov%2Flibarchivedd/lists"}