HTTP file reading helpers

This implements reading and seeking files and streams.

modules/access/http/file.c

+/*****************************************************************************
+ * file.h: HTTP read-only file
+ *****************************************************************************
+ * Copyright (C) 2015 Rémi Denis-Courmont
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2.1 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
+ *****************************************************************************/
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <vlc_common.h>
+#include <vlc_block.h>
+#include <vlc_url.h>
+#include <vlc_strings.h>
+#include "message.h"
+#include "connmgr.h"
+#include "file.h"
+
+#pragma GCC visibility push(default)
+
+struct vlc_http_file
+{
+    struct vlc_http_mgr *manager;
+    struct vlc_http_msg *resp;
+    char *host;
+    unsigned port;
+    char *authority;
+    char *path;
+    char *agent;
+    char *referrer;
+
+    uintmax_t offset;
+};
+
+static struct vlc_http_msg *vlc_http_file_req(const struct vlc_http_file *file,
+                                              uintmax_t offset)
+{
+    struct vlc_http_msg *req;
+    const char *str;
+
+    req = vlc_http_req_create("GET", "https", file->authority, file->path);
+    if (unlikely(req == NULL))
+        return NULL;
+
+    /* Content negotiation */
+    vlc_http_msg_add_header(req, "Accept", "*/*");
+
+    /* NOTE (TODO): Accept-Encoding should be used to allow compression.
+     * Unforunately, some servers do not send byte ranges when compression
+     * is enabled - so a separate HEAD request would be required first. */
+
+    const char *lang = vlc_gettext("C");
+    if (strcmp(lang, "C"))
+        vlc_http_msg_add_header(req, "Accept-Language",
+                                "%s, *;q=0.5", lang);
+
+    /* Authentication */
+    /* TODO: authentication */
+
+    /* Request context */
+    if (file->agent != NULL)
+        vlc_http_msg_add_agent(req, file->agent);
+
+    if (file->referrer != NULL) /* TODO: validate URL */
+        vlc_http_msg_add_header(req, "Referer", "%s", file->referrer);
+
+    if (file->resp != NULL
+     && (str = vlc_http_msg_get_header(file->resp, "ETag")))
+    {
+        if (!memcmp(str, "W/", 2))
+            str += 2; /* skip weak mark */
+        vlc_http_msg_add_header(req, "If-Match", "%s", str);
+    }
+
+    if (file->resp != NULL
+     && (str = vlc_http_msg_get_header(file->resp, "Date")))
+        vlc_http_msg_add_header(req, "If-Unmodified-Since", "%s", str);
+
+    if (vlc_http_msg_add_header(req, "Range", "bytes=%ju-", offset)
+     && offset != 0)
+        goto error;
+    /* TODO: vlc_http_msg_add_header(req, "TE", "deflate, gzip");*/
+    /* TODO: Cookies */
+    return req;
+error:
+    vlc_http_msg_destroy(req);
+    return NULL;
+}
+
+static struct vlc_http_msg *vlc_http_file_open(struct vlc_http_file *file,
+                                               uintmax_t offset)
+{
+    struct vlc_http_msg *req = vlc_http_file_req(file, offset);
+    if (unlikely(req == NULL))
+        return NULL;
+
+    struct vlc_http_msg *resp = vlc_https_request(file->manager, file->host,
+                                                  file->port, req);
+    vlc_http_msg_destroy(req);
+
+    resp = vlc_http_msg_get_final(resp);
+    if (resp == NULL)
+        return NULL;
+
+    int status = vlc_http_msg_get_status(resp);
+    if (status < 200 || status >= 599)
+    {
+        vlc_http_msg_destroy(resp);
+        resp = NULL;
+    }
+    return resp;
+}
+
+void vlc_http_file_destroy(struct vlc_http_file *file)
+{
+    if (file->resp != NULL)
+        vlc_http_msg_destroy(file->resp);
+
+    free(file->referrer);
+    free(file->agent);
+    free(file->path);
+    free(file->authority);
+    free(file->host);
+    free(file);
+}
+
+static char *vlc_http_authority(const char *host, unsigned port)
+{
+    static const char *const formats[4] = { "%s", "[%s]", "%s:%u", "[%s]:%u" };
+    const bool brackets = strchr(host, ':') != NULL;
+    const char *fmt = formats[brackets + 2 * (port != 0)];
+    char *authority;
+
+    if (unlikely(asprintf(&authority, fmt, host, port) == -1))
+        return NULL;
+    return authority;
+}
+
+struct vlc_http_file *vlc_http_file_create(struct vlc_http_mgr *mgr,
+                                           const char *uri, const char *ua,
+                                           const char *ref)
+{
+    vlc_url_t url;
+
+    vlc_UrlParse(&url, uri);
+    if (url.psz_protocol == NULL
+     || vlc_ascii_strcasecmp(url.psz_protocol, "https")
+     || url.psz_host == NULL)
+    {
+        vlc_UrlClean(&url);
+        return NULL;
+    }
+
+    struct vlc_http_file *file = malloc(sizeof (*file));
+    if (unlikely(file == NULL))
+    {
+        vlc_UrlClean(&url);
+        return NULL;
+    }
+
+    file->host = strdup(url.psz_host);
+    file->port = url.i_port;
+    file->authority = vlc_http_authority(url.psz_host, url.i_port);
+    file->agent = (ua != NULL) ? strdup(ua) : NULL;
+    file->referrer = (ref != NULL) ? strdup(ref) : NULL;
+
+    const char *path = url.psz_path;
+    if (path == NULL)
+        path = "/";
+
+    if (url.psz_option != NULL)
+    {
+        if (asprintf(&file->path, "%s?%s", path, url.psz_option) == -1)
+            file->path = NULL;
+    }
+    else
+        file->path = strdup(path);
+
+    vlc_UrlClean(&url);
+    file->manager = mgr;
+    file->resp = NULL;
+    file->offset = 0;
+
+    if (unlikely(file->host == NULL || file->authority == NULL
+              || file->path == NULL))
+    {
+        vlc_http_file_destroy(file);
+        file = NULL;
+    }
+    return file;
+}
+
+int vlc_http_file_get_status(struct vlc_http_file *file)
+{
+    if (file->resp == NULL)
+    {
+        file->resp = vlc_http_file_open(file, file->offset);
+        if (file->resp == NULL)
+            return -1;
+    }
+    return vlc_http_msg_get_status(file->resp);
+}
+
+char *vlc_http_file_get_redirect(struct vlc_http_file *file)
+{
+    int status = vlc_http_file_get_status(file);
+
+    /* TODO: if (status == 426 Upgrade Required) */
+
+    /* Location header is only meaningful for 201 and 3xx */
+    if (status != 201 && (status / 100) != 3)
+        return NULL;
+    if (status == 304 /* Not Modified */
+     || status == 305 /* Use Proxy (deprecated) */
+     || status == 306 /* Switch Proxy (former) */)
+        return NULL;
+
+    const char *location = vlc_http_msg_get_header(file->resp, "Location");
+    if (location == NULL)
+        return NULL;
+
+    /* TODO: if status is 3xx, check for Retry-After and wait */
+
+    /* NOTE: The anchor is discard if it is present as VLC does not support
+     * HTML anchors so far. */
+    size_t len = strcspn(location, "#");
+
+    /* FIXME: resolve relative URL _correctly_ */
+    if (location[0] == '/')
+    {
+        char *url;
+
+        if (unlikely(asprintf(&url, "https://%s%.*s", file->authority,
+                              (int)len, location)) < 0)
+            return NULL;
+        return url;
+    }
+    return strndup(location, len);
+}
+
+uintmax_t vlc_http_file_get_size(struct vlc_http_file *file)
+{
+    int status = vlc_http_file_get_status(file);
+    if (status < 0)
+        return -1;
+
+    const char *range = vlc_http_msg_get_header(file->resp, "Content-Range");
+
+    if (status == 206 /* Partial Content */)
+    {   /* IETF RFC7233 §4.1 */
+        if (range == NULL)
+            return -1; /* invalid response */
+
+        uintmax_t end, total;
+
+        switch (sscanf(range, "bytes %*u-%ju/%ju", &end, &total))
+        {
+            case 1:
+                if (unlikely(end == UINTMAX_MAX))
+                    return -1; /* avoid wrapping to zero */
+                return end + 1;
+            case 2:
+                return total;
+        }
+        return -1;
+    }
+
+    if (status == 416 /* Range Not Satisfiable */)
+    {   /* IETF RFC7233 §4.4 */
+        uintmax_t total;
+
+        if (range == NULL)
+            return -1; /* valid but helpless response */
+
+        if (sscanf(range, "bytes */%ju", &total) == 1)
+            return total; /* this occurs when seeking beyond EOF */
+    }
+
+    if (status >= 300 || status == 201)
+        return -1; /* Error or redirection, size is unknown/irrelevant. */
+
+    /* Content-Range is meaningless here (see RFC7233 B), so check if the size
+     * of the response entity body is known. */
+    return vlc_http_msg_get_size(file->resp);
+}
+
+bool vlc_http_file_can_seek(struct vlc_http_file *file)
+{   /* See IETF RFC7233 */
+    int status = vlc_http_file_get_status(file);
+    if (status < 0)
+        return false;
+    if (status == 206 || status == 416)
+        return true; /* Partial Content */
+
+    const char *str = vlc_http_msg_get_header(file->resp, "Accept-Ranges");
+    /* FIXME: tokenize */
+    if (str != NULL && !vlc_ascii_strcasecmp(str, "bytes"))
+        return true;
+
+    return false;
+}
+
+char *vlc_http_file_get_type(struct vlc_http_file *file)
+{
+    int status = vlc_http_file_get_status(file);
+    if (status < 200 || status >= 300)
+        return NULL;
+
+    const char *type = vlc_http_msg_get_header(file->resp, "Content-Type");
+    return (type != NULL) ? strdup(type) : NULL;
+}
+
+int vlc_http_file_seek(struct vlc_http_file *file, uintmax_t offset)
+{
+    struct vlc_http_msg *resp = vlc_http_file_open(file, offset);
+    if (resp == NULL)
+        return -1;
+
+    int status = vlc_http_msg_get_status(resp);
+    if (file->resp != NULL)
+    {   /* Accept the new and ditch the old one if:
+         * - requested succeeded and range was accepted (206),
+         * - requested failed due to out-of-range (416),
+         * - request succeeded and seek offset is zero (2xx).
+         */
+        if (status != 206 && status != 416 && (offset != 0 || status >= 300))
+        {
+            vlc_http_msg_destroy(resp);
+            return -1;
+        }
+        vlc_http_msg_destroy(file->resp);
+    }
+
+    file->resp = resp;
+    file->offset = offset;
+    return 0;
+}
+
+block_t *vlc_http_file_read(struct vlc_http_file *file)
+{
+    int status = vlc_http_file_get_status(file);
+    if (status < 200 || status >= 300)
+        return NULL; /* do not "read" redirect or error message */
+
+    block_t *block = vlc_http_msg_read(file->resp);
+    if (block == NULL)
+    {   /* Automatically reconnect if server supports seek */
+        if (vlc_http_file_can_seek(file)
+         && vlc_http_file_seek(file, file->offset) == 0)
+            block = vlc_http_msg_read(file->resp);
+
+        if (block == NULL)
+            return NULL;
+    }
+
+    file->offset += block->i_buffer;
+    return block;
+}

modules/access/http/file.h

+/*****************************************************************************
+ * file.h: HTTP read-only file
+ *****************************************************************************
+ * Copyright (C) 2015 Rémi Denis-Courmont
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2.1 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
+ *****************************************************************************/
+
+#include <stdint.h>
+
+struct vlc_http_file;
+struct vlc_http_mgr;
+struct block_t;
+
+struct vlc_http_file *vlc_http_file_create(struct vlc_http_mgr *mgr,
+                                           const char *url, const char *ua,
+                                           const char *ref);
+void vlc_http_file_destroy(struct vlc_http_file *file);
+
+int vlc_http_file_get_status(struct vlc_http_file *file);
+char *vlc_http_file_get_redirect(struct vlc_http_file *file);
+
+uintmax_t vlc_http_file_get_size(struct vlc_http_file *file);
+bool vlc_http_file_can_seek(struct vlc_http_file *file);
+char *vlc_http_file_get_type(struct vlc_http_file *file);
+int vlc_http_file_seek(struct vlc_http_file *file, uint64_t offset);
+struct block_t *vlc_http_file_read(struct vlc_http_file *file);