Add indexing of tarballs using libarchive; copyfile-aware

tar.c

@@ -0,0 +1,154 @@
+#include "pixz.h"
+
+#include <archive.h>
+#include <archive_entry.h>
+
+#include <sys/errno.h>
+#include <string.h>
+#include <libgen.h>
+
+
+// Tar uses records of 512 bytes
+#define CHUNKSIZE 512
+
+
+typedef struct pixz_tar_index_record pixz_tar_index_record;
+struct pixz_tar_index_record {
+    size_t offset;
+    char *name;
+    pixz_tar_index_record *next;
+};
+
+typedef struct {
+    pixz_tar_index_record *first;
+    pixz_tar_index_record *last;
+} pixz_tar_index;
+
+static pixz_tar_index *pixz_tar_index_new(void);
+static void pixz_tar_index_add(pixz_tar_index *i, size_t offset, const char *name);
+static void pixz_tar_index_dump(pixz_tar_index *i, FILE *out);
+static void pixz_tar_index_free(pixz_tar_index *i);
+static int pixz_tar_index_is_metadata(struct archive_entry *entry);
+
+
+typedef struct {
+    FILE *file;
+    uint8_t buf[CHUNKSIZE];
+} pixz_tar_input;
+
+static int pixz_tar_input_open(struct archive *a, void *refp);
+static int pixz_tar_input_close(struct archive *a, void *refp);
+static ssize_t pixz_tar_input_read(struct archive *a, void *refp, const void **buf);
+
+
+int main(void) {
+    pixz_tar_index *index = pixz_tar_index_new();
+    
+    struct archive *a = archive_read_new();
+    archive_read_support_compression_none(a);
+    archive_read_support_format_tar(a);
+    
+    pixz_tar_input input = { .file = stdin };    
+    if (archive_read_open(a, &input, pixz_tar_input_open, pixz_tar_input_read,
+            pixz_tar_input_close) != ARCHIVE_OK)
+        pixz_die("Can't open archive\n");
+    
+    int want_offset = 0;
+    size_t offset = 0;
+    while (1) {
+        struct archive_entry *entry;
+        int aerr = archive_read_next_header(a, &entry);
+        if (aerr == ARCHIVE_EOF)
+            break;
+        else if (aerr != ARCHIVE_OK)
+            pixz_die("Error reading header\n");
+        
+        if (!pixz_tar_index_is_metadata(entry)) {
+            const char *name = archive_entry_pathname(entry);        
+            pixz_tar_index_add(index, offset, name);
+            want_offset = 1;
+        }
+        
+        if (archive_read_data_skip(a) != ARCHIVE_OK)
+            pixz_die("Error skipping data\n");
+        
+        if (want_offset) {
+            offset = ftell(input.file);
+            want_offset = 0;
+        }
+    }
+    if (archive_read_finish(a) != ARCHIVE_OK)
+        pixz_die("Error finishing read\n");
+    
+    pixz_tar_index_dump(index, stdout);
+    pixz_tar_index_free(index);
+    
+    return 0;
+}
+
+
+static int pixz_tar_input_open(struct archive *a, void *refp) {
+    return ARCHIVE_OK;
+}
+
+static int pixz_tar_input_close(struct archive *a, void *refp) {
+    fclose(((pixz_tar_input*)refp)->file);
+    return ARCHIVE_OK;
+}
+
+static ssize_t pixz_tar_input_read(struct archive *a, void *refp, const void **buf) {
+    pixz_tar_input *input = (pixz_tar_input*)refp;
+    size_t rd = fread(input->buf, 1, CHUNKSIZE, input->file);
+    if (ferror(input->file)) {
+        archive_set_error(a, errno, "Read error");
+        return -1;
+    }
+    *buf = input->buf;
+    return rd;
+}
+
+
+static pixz_tar_index *pixz_tar_index_new(void) {
+    pixz_tar_index *i = malloc(sizeof(pixz_tar_index));
+    i->first = NULL;
+    i->last = NULL;
+    return i;
+}
+
+static void pixz_tar_index_add(pixz_tar_index *i, size_t offset, const char *name) {
+    pixz_tar_index_record *rec = malloc(sizeof(pixz_tar_index_record));
+    rec->next = NULL;
+    rec->name = strdup(name);
+    rec->offset = offset;
+    
+    if (!i->first)
+        i->first = rec;
+    if (i->last)
+        i->last->next = rec;
+    i->last = rec;
+}
+
+static void pixz_tar_index_dump(pixz_tar_index *i, FILE *out) {
+    for (pixz_tar_index_record *rec = i->first; rec; rec = rec->next) {
+        fprintf(out, "%12zu  %s\n", rec->offset, rec->name);
+    }
+}
+
+static void pixz_tar_index_free(pixz_tar_index *i) {
+    for (pixz_tar_index_record *rec = i->first; rec; rec = rec->next) {
+        free(rec->name);
+        free(rec);
+    }
+    free(i);
+}
+
+static int pixz_tar_index_is_metadata(struct archive_entry *entry) {
+    // FIXME: better copyfile detection?
+    
+    const char *name = archive_entry_pathname(entry);
+    size_t i = strlen(name);
+    while (i != 0 && name[i - 1] != '/')
+        --i;
+    
+    return strncmp(name + i, "._", 2) == 0;
+}

util.c

@@ -0,0 +1,12 @@
+#include "pixz.h"
+
+#include <stdarg.h>
+
+void pixz_die(const char *fmt, ...) {
+    va_list args;
+    va_start(args, fmt);
+    vfprintf(stderr, fmt, args);
+    fflush(stderr);
+    va_end(args);
+    exit(1);
+}