Add tar container format

diff --git a/Makefile b/Makefile
index 288190d..3183e71 100644
--- a/Makefile
+++ b/Makefile
@@ -73,7 +73,7 @@  block-obj-$(CONFIG_AIO) += posix-aio-compat.o
 
 block-nested-y += cow.o qcow.o vmdk.o cloop.o dmg.o bochs.o vpc.o vvfat.o
 block-nested-y += qcow2.o qcow2-refcount.o qcow2-cluster.o qcow2-snapshot.o
-block-nested-y += parallels.o nbd.o dictzip.o
+block-nested-y += parallels.o nbd.o dictzip.o tar.o
 block-nested-$(CONFIG_WIN32) += raw-win32.o
 block-nested-$(CONFIG_POSIX) += raw-posix.o
 block-nested-$(CONFIG_CURL) += curl.o
diff --git a/block/tar.c b/block/tar.c
new file mode 100644
index 0000000..2c965cc
--- /dev/null
+++ b/block/tar.c
@@ -0,0 +1,326 @@ 
+/*
+ * Tar block driver
+ *
+ * Copyright (c) 2009 Alexander Graf <agraf@suse.de>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "qemu-common.h"
+#include "block_int.h"
+
+// #define DEBUG
+
+#ifdef DEBUG
+#define dprintf(fmt, ...) do { printf("tar: " fmt, ## __VA_ARGS__); } while (0)
+#else
+#define dprintf(fmt, ...) do { } while (0)
+#endif
+
+#define SECTOR_SIZE      512
+
+#define POSIX_TAR_MAGIC  "ustar"
+#define OFFS_LENGTH      0x7c
+#define OFFS_TYPE        0x9c
+#define OFFS_MAGIC       0x101
+
+#define OFFS_S_SP        0x182
+#define OFFS_S_EXT       0x1e2
+#define OFFS_S_LENGTH    0x1e3
+#define OFFS_SX_EXT      0x1f8
+
+typedef struct SparseCache {
+    uint64_t start;
+    uint64_t end;
+} SparseCache;
+
+typedef struct BDRVTarState {
+    BlockDriverState *hd;
+    size_t file_sec;
+    uint64_t file_len;
+    SparseCache *sparse;
+    int sparse_num;
+    uint64_t last_end;
+} BDRVTarState;
+
+static int tar_probe(const uint8_t *buf, int buf_size, const char *filename)
+{
+    if (buf_size < OFFS_MAGIC + 5)
+        return 0;
+
+    /* we only support newer tar */
+    if (!strncmp((char*)buf + OFFS_MAGIC, POSIX_TAR_MAGIC, 5))
+        return 100;
+
+    return 0;
+}
+
+static int str_ends(char *str, const char *end)
+{
+    int end_len = strlen(end);
+    int str_len = strlen(str);
+
+    if (str_len < end_len)
+        return 0;
+
+    return !strncmp(str + str_len - end_len, end, end_len);
+}
+
+static int is_target_file(BlockDriverState *bs, char *filename)
+{
+    int retval = 0;
+
+    if (str_ends(filename, ".raw"))
+        retval = 1;
+
+    if (str_ends(filename, ".qcow"))
+        retval = 1;
+
+    if (str_ends(filename, ".qcow2"))
+        retval = 1;
+
+    if (str_ends(filename, ".vmdk"))
+        retval = 1;
+
+    dprintf("does filename %s match? %s\n", filename, retval ? "yes" : "no");
+    return retval;
+}
+
+static uint64_t tar2u64(char *ptr)
+{
+    uint64_t retval;
+    char oldend = ptr[12];
+
+    ptr[12] = '\0';
+    if (*ptr & 0x80)
+        retval = be64_to_cpu(*(uint64_t *)ptr);
+    else
+        retval = strtol(ptr, NULL, 8);
+
+    ptr[12] = oldend;
+
+    dprintf("Convert %s -> %#lx\n", ptr, retval);
+    return retval;
+}
+
+static void tar_sparse(BDRVTarState *s, uint64_t offs, uint64_t len)
+{
+    SparseCache *sparse;
+
+    if (!len)
+        return;
+    if (!(offs - s->last_end)) {
+        s->last_end += len;
+        return;
+    }
+    if (s->last_end > offs)
+        return;
+
+    dprintf("Last chunk until %lx new chunk at %lx\n", s->last_end, offs);
+
+    s->sparse = qemu_realloc(s->sparse, (s->sparse_num + 1) * sizeof(SparseCache));
+    sparse = &s->sparse[s->sparse_num];
+    sparse->start = s->last_end;
+    sparse->end = offs;
+    s->last_end = offs + len;
+    s->sparse_num++;
+    dprintf("Sparse at %lx end=%lx\n", sparse->start,
+                                       sparse->end);
+}
+
+static int tar_open(BlockDriverState *bs, const char *filename, int flags)
+{
+    BDRVTarState *s = bs->opaque;
+    char header[SECTOR_SIZE];
+    char *magic;
+    size_t header_offs = 0;
+    int ret;
+
+    ret = bdrv_file_open(&s->hd, filename, flags);
+    if (ret < 0)
+        return ret;
+
+    /* Search the file for an image */
+
+    do {
+        /* tar header */
+        if (bdrv_pread(s->hd, header_offs, header, SECTOR_SIZE) != SECTOR_SIZE)
+            goto fail;
+
+        if ((header_offs > 1) && !header[0]) {
+            fprintf(stderr, "Tar: No image file found in archive\n");
+            goto fail;
+        }
+
+        magic = &header[OFFS_MAGIC];
+        if (strncmp(magic, POSIX_TAR_MAGIC, 5)) {
+            fprintf(stderr, "Tar: Invalid magic: %s\n", magic);
+            goto fail;
+        }
+
+        dprintf("file type: %c\n", header[OFFS_TYPE]);
+
+        /* file length*/
+        s->file_len = (tar2u64(&header[OFFS_LENGTH]) + (SECTOR_SIZE - 1)) &
+                      ~(SECTOR_SIZE - 1);
+        s->file_sec = (header_offs / SECTOR_SIZE) + 1;
+
+        header_offs += s->file_len + SECTOR_SIZE;
+    } while(!is_target_file(bs, header));
+
+    /* We found an image! */
+
+    if (header[OFFS_TYPE] == 'S') {
+        uint8_t isextended;
+        int i;
+
+        for (i = OFFS_S_SP; i < (OFFS_S_SP + (4 * 24)); i += 24)
+            tar_sparse(s, tar2u64(&header[i]), tar2u64(&header[i+12]));
+
+        s->file_len = tar2u64(&header[OFFS_S_LENGTH]);
+        isextended = header[OFFS_S_EXT];
+
+        while (isextended) {
+            if (bdrv_pread(s->hd, s->file_sec * SECTOR_SIZE, header,
+                           SECTOR_SIZE) != SECTOR_SIZE)
+                goto fail;
+
+            for (i = 0; i < (21 * 24); i += 24)
+                tar_sparse(s, tar2u64(&header[i]), tar2u64(&header[i+12]));
+            isextended = header[OFFS_SX_EXT];
+            s->file_sec++;
+        }
+        tar_sparse(s, s->file_len, 1);
+    }
+
+    return 0;
+
+fail:
+    fprintf(stderr, "Tar: Error opening file\n");
+    bdrv_delete(s->hd);
+    return -EINVAL;
+}
+
+typedef struct TarAIOCB {
+    BlockDriverAIOCB common;
+    QEMUBH *bh;
+} TarAIOCB;
+
+static AIOPool tar_aio_pool = {
+    .aiocb_size         = sizeof(TarAIOCB),
+};
+
+/* This callback gets invoked when we have pure sparseness */
+static void tar_sparse_cb(void *opaque)
+{
+    TarAIOCB *acb = (TarAIOCB *)opaque;
+
+    acb->common.cb(acb->common.opaque, 0);
+    qemu_bh_delete(acb->bh);
+    qemu_aio_release(acb);
+}
+
+/* This is where we get a request from a caller to read something */
+static BlockDriverAIOCB *tar_aio_readv(BlockDriverState *bs,
+        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
+        BlockDriverCompletionFunc *cb, void *opaque)
+{
+    BDRVTarState *s = bs->opaque;
+    SparseCache *sparse;
+    int64_t sec_file = sector_num + s->file_sec;
+    int64_t start = sector_num * SECTOR_SIZE;
+    int64_t end = start + (nb_sectors * SECTOR_SIZE);
+    int i;
+    TarAIOCB *acb;
+
+    for (i = 0; i < s->sparse_num; i++) {
+        sparse = &s->sparse[i];
+        if (sparse->start > end) {
+            /* We expect the cache to be start increasing */
+            break;
+        } else if ((sparse->start < start) && (sparse->end <= start)) {
+            /* sparse before our offset */
+            sec_file -= (sparse->end - sparse->start) / SECTOR_SIZE;
+        } else if ((sparse->start <= start) && (sparse->end >= end)) {
+            /* all our sectors are sparse */
+            char *buf = qemu_mallocz(nb_sectors * SECTOR_SIZE);
+
+            acb = qemu_aio_get(&tar_aio_pool, bs, cb, opaque);
+            qemu_iovec_from_buffer(qiov, buf, nb_sectors * SECTOR_SIZE);
+            qemu_free(buf);
+            acb->bh = qemu_bh_new(tar_sparse_cb, acb);
+            qemu_bh_schedule(acb->bh);
+
+            return &acb->common;
+        } else if (((sparse->start >= start) && (sparse->start < end)) ||
+                   ((sparse->end >= start) && (sparse->end < end))) {
+            /* we're semi-sparse (worst case) */
+            /* let's go synchronous and read all sectors individually */
+            char *buf = qemu_malloc(nb_sectors * SECTOR_SIZE);
+            uint64_t offs;
+
+            for (offs = 0; offs < (nb_sectors * SECTOR_SIZE);
+                 offs += SECTOR_SIZE) {
+                bdrv_pread(bs, (sector_num * SECTOR_SIZE) + offs,
+                           buf + offs, SECTOR_SIZE);
+            }
+
+            qemu_iovec_from_buffer(qiov, buf, nb_sectors * SECTOR_SIZE);
+            acb = qemu_aio_get(&tar_aio_pool, bs, cb, opaque);
+            acb->bh = qemu_bh_new(tar_sparse_cb, acb);
+            qemu_bh_schedule(acb->bh);
+
+            return &acb->common;
+        }
+    }
+
+    return bdrv_aio_readv(s->hd, sec_file, qiov, nb_sectors,
+                          cb, opaque);
+}
+
+static void tar_close(BlockDriverState *bs)
+{
+    dprintf("Close\n");
+}
+
+static int64_t tar_getlength(BlockDriverState *bs)
+{
+    BDRVTarState *s = bs->opaque;
+    dprintf("getlength -> %ld\n", s->file_len);
+    return s->file_len;
+}
+
+static BlockDriver bdrv_tar = {
+    .format_name     = "tar",
+
+    .instance_size   = sizeof(BDRVTarState),
+    .bdrv_open       = tar_open,
+    .bdrv_close      = tar_close,
+    .bdrv_getlength  = tar_getlength,
+    .bdrv_probe      = tar_probe,
+
+    .bdrv_aio_readv  = tar_aio_readv,
+};
+
+static void tar_block_init(void)
+{
+    bdrv_register(&bdrv_tar);
+}
+
+block_init(tar_block_init);