First try to get duration from a kara (WIP)

inc/lektor/mkv.h

@@ -47,6 +47,10 @@ struct kara {
    Returns 0 on success and -1 on error. */
 int kara_metadata_read(struct kara_metadata *dst, const char *filename);
 
+/* Reads the duration of the .mkv file `filename`. Returns 0 on success
+   and -1 on error. */
+int kara_read_length(size_t *len, const char *filename);
+
 /* Write metadata to a mkv file. Returns 0 on success and -1 on error */
 int kara_metadata_write(struct kara_metadata *mdt, const char *filename, const char *mkvpropedit);
 

meson.build

@@ -166,6 +166,12 @@ lkt = executable( 'lkt'
                 , include_directories: includes
                 , install: true )
 
+debug = executable( 'lkt-debug'
+                  , files('src/main/debug.c')
+                  , include_directories: includes
+                  , dependencies: [ bin_deps ]
+                  )
+
 # Man pages
 man_sh     = find_program('scripts/man.sh')
 man_header = run_command('realpath', 'doc/header').stdout().strip()

src/main/debug.c

+#include <lektor/mkv.h>
+#include <stdio.h>
+
+int
+main(int argc, char **argv)
+{
+    size_t len = 0;
+
+    if (argc != 2)
+        return 1;
+
+    if (kara_read_length(&len, argv[1]) < 0)
+        return 2;
+
+    printf("Kara length: %ld\n", len);
+    return 0;
+}

src/mkv/mkv.c

@@ -7,6 +7,7 @@
 #include <string.h>
 #include <strings.h>
 #include <unistd.h>
+#include <errno.h>
 
 #include <common/bufferfd.h>
 #include <lektor/mkv.h>
@@ -401,7 +402,7 @@ mkv_read_tag(struct bufferfd *bf, struct mkv_tag *res)
 }
 
 static ssize_t
-mkv_seek_tags(struct bufferfd *bf, size_t header_len)
+mkv_seek(struct bufferfd *bf, size_t header_len, size_t what)
 {
     uint64_t seekhead_len;
 
@@ -430,7 +431,7 @@ mkv_seek_tags(struct bufferfd *bf, size_t header_len)
 
         seekhead_len -= n;
 
-        if (eid == EBML_MKV_SEEK && s.id == EBML_MKV_TAGS)
+        if (eid == EBML_MKV_SEEK && s.id == what)
             return bufferfd_seek(bf, s.pos + header_len);
     }
 
@@ -497,17 +498,113 @@ kara_read_tags(struct bufferfd *bf, struct kara_metadata *dst)
     return 0;
 }
 
+static int
+kara_read_segment(struct bufferfd *bf, size_t *len)
+{
+    /* TODO: Read correct elements, Duration and TimestampScale,
+       the result will be `*len = Duration * TimestampScale`. */
+    uint64_t data_len;
+
+    if (mkv_read_element_length(bf, &data_len) < 0)
+        return -1;
+
+    while (data_len > 0) {
+        ssize_t n;
+        uint32_t eid;
+        uint64_t elen;
+
+        if ((n = mkv_read_element_id(bf, &eid)) < 0 || eid != EBML_MKV_SEGMENT)
+            return -1;
+
+        data_len -= n;
+
+        if ((n = mkv_read_element_length(bf, &elen)) < 0)
+            return -1;
+
+        data_len -= n;
+
+        /* Find what we need */
+
+        if (eid == EBML_MKV_SEG_DURATION ||
+            eid == EBML_MKV_SEG_TS_SCALE) {
+            switch (*len) {
+            case 0:
+                *len = 1;
+                /* Fallthrough */
+            default:
+                printf("Len: %ld\n", n);
+                *len *= 1;
+            }
+        }
+    }
+
+    return 0;
+}
+
+int
+kara_read_length(size_t *len, const char *filename)
+{
+    errno = 0;
+    int status_code = -1;
+    struct bufferfd file = {
+        .len = 0,
+        .pos = 0,
+        .fd = open(filename, O_RDONLY),
+    };
+
+    if (file.fd < 0) {
+        LOG_ERROR("MKV", "Faield to open file '%s': %s",
+                  filename, strerror(errno));
+        return -1;
+    }
+
+    uint32_t eid;
+    uint64_t elength;
+    ssize_t header_len = mkv_skip_header(&file);
+
+    if (header_len < 0)
+        goto error;
+
+    *len = 0;
+
+    for (;;) {
+        if (mkv_read_element_id(&file, &eid) < 0)
+            goto error;
+
+        if (eid == EBML_MKV_SEEKHEAD) {
+            if (mkv_seek(&file, (size_t) header_len, (size_t) EBML_MKV_SEGMENT) < 0)
+                goto error;
+        } else if (eid == EBML_MKV_SEGMENT) {
+            if (kara_read_segment(&file, len) < 0)
+                goto error;
+            break;
+        } else {
+            if (mkv_read_element_length(&file, &elength) < 0)
+                goto error;
+            if (bufferfd_skip(&file, elength) < 0)
+                goto error;
+        }
+    }
+
+    status_code = 0;
+error:
+    close(file.fd);
+    return status_code;
+}
+
 int
 kara_metadata_read(struct kara_metadata *dst, const char *filename)
 {
     int status_code = -1;
     struct bufferfd file;
+    errno = 0;
     file.len = 0;
     file.pos = 0;
     file.fd = open(filename, O_RDONLY);
 
     if (file.fd < 0) {
-        perror("Failed to open file");
+        LOG_ERROR("MKV", "Failed to open file '%s': %s",
+                  filename, strerror(errno));
         return -1;
     }
 
@@ -525,7 +622,7 @@ kara_metadata_read(struct kara_metadata *dst, const char *filename)
             goto error;
 
         if (eid == EBML_MKV_SEEKHEAD) {
-            if (mkv_seek_tags(&file, (size_t) header_len) < 0)
+            if (mkv_seek(&file, (size_t) header_len, (size_t) EBML_MKV_TAGS) < 0)
                 goto error;
         } else if (eid == EBML_MKV_TAGS) {
             if (kara_read_tags(&file, dst) < 0)