No code uses this yet.

Signed-off-by: Ethan Glasser-Camp <ethan@betacantrips.com>
---
 lib/mailstore.c |  117 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 116 insertions(+), 1 deletion(-)

diff --git a/lib/mailstore.c b/lib/mailstore.c
index 48acd47..a29d734 100644
--- a/lib/mailstore.c
+++ b/lib/mailstore.c
@@ -17,18 +17,133 @@
  *
  * Author: Carl Worth <cworth@cworth.org>
  */
+#include <uriparser/Uri.h>
 #include <stdio.h>
+#include <glib.h>
 
 #include "notmuch-private.h"
 
+static FILE *
+notmuch_mailstore_basic_open (const char *filename)
+{
+    return fopen (filename, "r");
+}
+
+/* Since we have to return a FILE*, we use fmemopen to turn buffers
+ * into FILE* streams. But when we close these streams, we have to
+ * free() the buffers. Use a hash to associate the two.
+ */
+static GHashTable *_mbox_files_to_strings = NULL;
+
+static void
+_ensure_mbox_files_to_strings () {
+    if (_mbox_files_to_strings == NULL)
+        _mbox_files_to_strings = g_hash_table_new (NULL, NULL);
+}
+
+static FILE *
+notmuch_mailstore_mbox_open (UriUriA *uri)
+{
+    FILE *ret = NULL, *mbox = NULL;
+    char *filename, *message, *length_s;
+    const char *error;
+    long int offset, length, this_read;
+    _ensure_mbox_files_to_strings ();
+
+    offset = strtol (uri->fragment.first, &length_s, 10);
+    length = strtol (length_s+1, NULL, 10);
+
+    filename = talloc_strndup (NULL, uri->pathHead->text.first-1,
+                               uri->pathTail->text.afterLast-uri->pathHead->text.first+1);
+
+    if (filename == NULL)
+        goto DONE;
+
+    mbox = fopen (filename, "r");
+    if (mbox == NULL) {
+        fprintf (stderr, "Couldn't open message %s: %s.\n", uri->scheme.first,
+                 strerror (errno));
+        goto DONE;
+    }
+
+    message = talloc_array (NULL, char, length);
+    fseek (mbox, offset, SEEK_SET);
+
+    this_read = fread (message, sizeof(char), length, mbox);
+    if (this_read != length) {
+        if (feof (mbox))
+            error = "end of file reached";
+        if (ferror (mbox))
+            error = strerror (ferror (mbox));
+
+        fprintf (stderr, "Couldn't read message %s: %s.\n", uri->scheme.first, error);
+        goto DONE;
+    }
+
+    ret = fmemopen (message, length, "r");
+    if (ret == NULL) {
+        /* No fclose will ever be called, so let's free message now */
+        talloc_free (message);
+        goto DONE;
+    }
+
+    g_hash_table_insert (_mbox_files_to_strings, ret, message);
+DONE:
+    if (filename)
+        talloc_free (filename);
+    if (mbox)
+        fclose (mbox);
+
+    return ret;
+}
+
 FILE *
 notmuch_mailstore_open (const char *filename)
 {
-    return fopen (filename, "r");
+    FILE *ret = NULL;
+    UriUriA parsed;
+    UriParserStateA state;
+    state.uri = &parsed;
+    if (uriParseUriA (&state, filename) != URI_SUCCESS) {
+        /* Failure. Fall back to fopen and hope for the best. */
+        ret = notmuch_mailstore_basic_open (filename);
+        goto DONE;
+    }
+
+    if (parsed.scheme.first == NULL) {
+        /* No scheme. Probably not really a URL but just an ordinary
+         * filename, such as a Maildir message. */
+        ret = notmuch_mailstore_basic_open (filename);
+        goto DONE;
+    }
+
+    if (0 == strncmp (parsed.scheme.first, "mbox",
+                      parsed.scheme.afterLast-parsed.scheme.first)) {
+        /* mbox URI of the form mbox:///path/to/file#offset+length.
+         * Just pass the parsed URI. */
+        ret = notmuch_mailstore_mbox_open (&parsed);
+        goto DONE;
+    }
+
+    /* Default case */
+    fprintf (stderr, "Error: Could not open URI %s: unknown scheme.\n",
+             filename);
+
+DONE:
+    uriFreeUriMembersA (&parsed);
+    return ret;
 }
 
 int
 notmuch_mailstore_close (FILE *file)
 {
+    char *file_buffer;
+    if (_mbox_files_to_strings != NULL) {
+        file_buffer = g_hash_table_lookup (_mbox_files_to_strings, file);
+        if (file_buffer != NULL)
+            talloc_free (file_buffer);
+
+        g_hash_table_remove (_mbox_files_to_strings, file);
+    }
     return fclose (file);
 }
-- 
1.7.9.5