PHP 語言 exif_read_data 函式部份的原始碼

處理手機上傳圖片時，偶爾會遇到的旋轉問題

在 PHP 需要使用 exif_read_data 去確認拍照時的角度，好奇 exif_read_data 的原始碼

查了一下，發現函式內容在這裡：

https://github.com/php/php-src/blob/master/ext/exif/exif.c

/* {{{ proto array exif_read_data(mixed stream [, string sections_needed [, bool sub_arrays[, bool read_thumbnail]]])
   Reads header data from an image and optionally reads the internal thumbnails */
PHP_FUNCTION(exif_read_data)
{
    zend_string *z_sections_needed = NULL;
    zend_bool sub_arrays = 0, read_thumbnail = 0, read_all = 0;
    zval *stream;
    int i, ret, sections_needed = 0;
    image_info_type ImageInfo;
    char tmp[64], *sections_str, *s;

    /* Parse arguments */
    ZEND_PARSE_PARAMETERS_START(1, 4)
        Z_PARAM_ZVAL(stream)
        Z_PARAM_OPTIONAL
        Z_PARAM_STR(z_sections_needed)
        Z_PARAM_BOOL(sub_arrays)
        Z_PARAM_BOOL(read_thumbnail)
    ZEND_PARSE_PARAMETERS_END();

    memset(&ImageInfo, 0, sizeof(ImageInfo));

    if (z_sections_needed) {
        spprintf(&sections_str, 0, ",%s,", ZSTR_VAL(z_sections_needed));
        /* sections_str DOES start with , and SPACES are NOT allowed in names */
        s = sections_str;
        while (*++s) {
            if (*s == ' ') {
                *s = ',';
            }
        }

        for (i = 0; i < SECTION_COUNT; i++) {
            snprintf(tmp, sizeof(tmp), ",%s,", exif_get_sectionname(i));
            if (strstr(sections_str, tmp)) {
                sections_needed |= 1<<i;
            }
        }
        EFREE_IF(sections_str);
        /* now see what we need */
#ifdef EXIF_DEBUG
        sections_str = exif_get_sectionlist(sections_needed);
        if (!sections_str) {
            RETURN_FALSE;
        }
        exif_error_docref(NULL EXIFERR_CC, &ImageInfo, E_NOTICE, "Sections needed: %s", sections_str[0] ? sections_str : "None");
        EFREE_IF(sections_str);
#endif
    }

    if (Z_TYPE_P(stream) == IS_RESOURCE) {
        php_stream *p_stream = NULL;

        php_stream_from_res(p_stream, Z_RES_P(stream));

        ret = exif_read_from_stream(&ImageInfo, p_stream, read_thumbnail, read_all);
    } else {
        convert_to_string(stream);

        if (!Z_STRLEN_P(stream)) {
            exif_error_docref(NULL EXIFERR_CC, &ImageInfo, E_WARNING, "Filename cannot be empty");

            RETURN_FALSE;
        }

        ret = exif_read_from_file(&ImageInfo, Z_STRVAL_P(stream), read_thumbnail, read_all);
    }

    sections_str = exif_get_sectionlist(ImageInfo.sections_found);

#ifdef EXIF_DEBUG
    if (sections_str) {
        exif_error_docref(NULL EXIFERR_CC, &ImageInfo, E_NOTICE, "Sections found: %s", sections_str[0] ? sections_str : "None");
    }
#endif

    ImageInfo.sections_found |= FOUND_COMPUTED|FOUND_FILE;/* do not inform about in debug*/

    if (ret == FALSE || (sections_needed && !(sections_needed&ImageInfo.sections_found))) {
        /* array_init must be checked at last! otherwise the array must be freed if a later test fails. */
        exif_discard_imageinfo(&ImageInfo);
        EFREE_IF(sections_str);
        RETURN_FALSE;
    }

    array_init(return_value);

#ifdef EXIF_DEBUG
    exif_error_docref(NULL EXIFERR_CC, &ImageInfo, E_NOTICE, "Generate section FILE");
#endif

    /* now we can add our information */
    exif_iif_add_str(&ImageInfo, SECTION_FILE, "FileName",      ImageInfo.FileName);
    exif_iif_add_int(&ImageInfo, SECTION_FILE, "FileDateTime",  ImageInfo.FileDateTime);
    exif_iif_add_int(&ImageInfo, SECTION_FILE, "FileSize",      ImageInfo.FileSize);
    exif_iif_add_int(&ImageInfo, SECTION_FILE, "FileType",      ImageInfo.FileType);
    exif_iif_add_str(&ImageInfo, SECTION_FILE, "MimeType",      (char*)php_image_type_to_mime_type(ImageInfo.FileType));
    exif_iif_add_str(&ImageInfo, SECTION_FILE, "SectionsFound", sections_str ? sections_str : "NONE");

#ifdef EXIF_DEBUG
    exif_error_docref(NULL EXIFERR_CC, &ImageInfo, E_NOTICE, "Generate section COMPUTED");
#endif

    if (ImageInfo.Width>0 &&  ImageInfo.Height>0) {
        exif_iif_add_fmt(&ImageInfo, SECTION_COMPUTED, "html"   , "width=\"%d\" height=\"%d\"", ImageInfo.Width, ImageInfo.Height);
        exif_iif_add_int(&ImageInfo, SECTION_COMPUTED, "Height", ImageInfo.Height);
        exif_iif_add_int(&ImageInfo, SECTION_COMPUTED, "Width",  ImageInfo.Width);
    }
    exif_iif_add_int(&ImageInfo, SECTION_COMPUTED, "IsColor", ImageInfo.IsColor);
    if (ImageInfo.motorola_intel != -1) {
        exif_iif_add_int(&ImageInfo, SECTION_COMPUTED, "ByteOrderMotorola", ImageInfo.motorola_intel);
    }
    if (ImageInfo.FocalLength) {
        exif_iif_add_fmt(&ImageInfo, SECTION_COMPUTED, "FocalLength", "%4.1Fmm", ImageInfo.FocalLength);
        if(ImageInfo.CCDWidth) {
            exif_iif_add_fmt(&ImageInfo, SECTION_COMPUTED, "35mmFocalLength", "%dmm", (int)(ImageInfo.FocalLength/ImageInfo.CCDWidth*35+0.5));
        }
    }
    if(ImageInfo.CCDWidth) {
        exif_iif_add_fmt(&ImageInfo, SECTION_COMPUTED, "CCDWidth", "%dmm", (int)ImageInfo.CCDWidth);
    }
    if(ImageInfo.ExposureTime>0) {
        if(ImageInfo.ExposureTime <= 0.5) {
            exif_iif_add_fmt(&ImageInfo, SECTION_COMPUTED, "ExposureTime", "%0.3F s (1/%d)", ImageInfo.ExposureTime, (int)(0.5 + 1/ImageInfo.ExposureTime));
        } else {
            exif_iif_add_fmt(&ImageInfo, SECTION_COMPUTED, "ExposureTime", "%0.3F s", ImageInfo.ExposureTime);
        }
    }
    if(ImageInfo.ApertureFNumber) {
        exif_iif_add_fmt(&ImageInfo, SECTION_COMPUTED, "ApertureFNumber", "f/%.1F", ImageInfo.ApertureFNumber);
    }
    if(ImageInfo.Distance) {
        if(ImageInfo.Distance<0) {
            exif_iif_add_str(&ImageInfo, SECTION_COMPUTED, "FocusDistance", "Infinite");
        } else {
            exif_iif_add_fmt(&ImageInfo, SECTION_COMPUTED, "FocusDistance", "%0.2Fm", ImageInfo.Distance);
        }
    }
    if (ImageInfo.UserComment) {
        exif_iif_add_buffer(&ImageInfo, SECTION_COMPUTED, "UserComment", ImageInfo.UserCommentLength, ImageInfo.UserComment);
        if (ImageInfo.UserCommentEncoding && strlen(ImageInfo.UserCommentEncoding)) {
            exif_iif_add_str(&ImageInfo, SECTION_COMPUTED, "UserCommentEncoding", ImageInfo.UserCommentEncoding);
        }
    }

    exif_iif_add_str(&ImageInfo, SECTION_COMPUTED, "Copyright",              ImageInfo.Copyright);
    exif_iif_add_str(&ImageInfo, SECTION_COMPUTED, "Copyright.Photographer", ImageInfo.CopyrightPhotographer);
    exif_iif_add_str(&ImageInfo, SECTION_COMPUTED, "Copyright.Editor",       ImageInfo.CopyrightEditor);

    for (i=0; i<ImageInfo.xp_fields.count; i++) {
        exif_iif_add_str(&ImageInfo, SECTION_WINXP, exif_get_tagname(ImageInfo.xp_fields.list[i].tag, NULL, 0, exif_get_tag_table(SECTION_WINXP)), ImageInfo.xp_fields.list[i].value);
    }
    if (ImageInfo.Thumbnail.size) {
        if (read_thumbnail) {
            /* not exif_iif_add_str : this is a buffer */
            exif_iif_add_tag(&ImageInfo, SECTION_THUMBNAIL, "THUMBNAIL", TAG_NONE, TAG_FMT_UNDEFINED, ImageInfo.Thumbnail.size, ImageInfo.Thumbnail.data, ImageInfo.Thumbnail.size);
        }
        if (!ImageInfo.Thumbnail.width || !ImageInfo.Thumbnail.height) {
            /* try to evaluate if thumbnail data is present */
            exif_scan_thumbnail(&ImageInfo);
        }
        exif_iif_add_int(&ImageInfo, SECTION_COMPUTED, "Thumbnail.FileType", ImageInfo.Thumbnail.filetype);
        exif_iif_add_str(&ImageInfo, SECTION_COMPUTED, "Thumbnail.MimeType", (char*)php_image_type_to_mime_type(ImageInfo.Thumbnail.filetype));
    }
    if (ImageInfo.Thumbnail.width && ImageInfo.Thumbnail.height) {
        exif_iif_add_int(&ImageInfo, SECTION_COMPUTED, "Thumbnail.Height", ImageInfo.Thumbnail.height);
        exif_iif_add_int(&ImageInfo, SECTION_COMPUTED, "Thumbnail.Width",  ImageInfo.Thumbnail.width);
    }
    EFREE_IF(sections_str);

#ifdef EXIF_DEBUG
    exif_error_docref(NULL EXIFERR_CC, &ImageInfo, E_NOTICE, "Adding image infos");
#endif

    add_assoc_image_info(return_value, sub_arrays, &ImageInfo, SECTION_FILE      );
    add_assoc_image_info(return_value, 1,          &ImageInfo, SECTION_COMPUTED  );
    add_assoc_image_info(return_value, sub_arrays, &ImageInfo, SECTION_ANY_TAG   );
    add_assoc_image_info(return_value, sub_arrays, &ImageInfo, SECTION_IFD0      );
    add_assoc_image_info(return_value, 1,          &ImageInfo, SECTION_THUMBNAIL );
    add_assoc_image_info(return_value, 1,          &ImageInfo, SECTION_COMMENT   );
    add_assoc_image_info(return_value, sub_arrays, &ImageInfo, SECTION_EXIF      );
    add_assoc_image_info(return_value, sub_arrays, &ImageInfo, SECTION_GPS       );
    add_assoc_image_info(return_value, sub_arrays, &ImageInfo, SECTION_INTEROP   );
    add_assoc_image_info(return_value, sub_arrays, &ImageInfo, SECTION_FPIX      );
    add_assoc_image_info(return_value, sub_arrays, &ImageInfo, SECTION_APP12     );
    add_assoc_image_info(return_value, sub_arrays, &ImageInfo, SECTION_WINXP     );
    add_assoc_image_info(return_value, sub_arrays, &ImageInfo, SECTION_MAKERNOTE );

#ifdef EXIF_DEBUG
    exif_error_docref(NULL EXIFERR_CC, &ImageInfo, E_NOTICE, "Discarding info");
#endif

    exif_discard_imageinfo(&ImageInfo);

#ifdef EXIF_DEBUG
    php_error_docref1(NULL, (Z_TYPE_P(stream) == IS_RESOURCE ? "<stream>" : Z_STRVAL_P(stream)), E_NOTICE, "Done");
#endif
}
/* }}} */

不熟 C 的話，這不太好讀

不過可以去看相關的 tests

https://github.com/php/php-src/tree/master/ext/exif/tests

檔案架構很漂亮，很多測試，每個新的 bug 會有對應的檔案來測試處理