header.c, lookup_table.c: Read/write data from structures
[wimlib] / src / header.c
index c0518ecbabb820bec1933cc5c91d18aeb77173a7..0066d75a3ba7b6d9d5db40a506c4fb9b75154327 100644 (file)
@@ -29,7 +29,7 @@
 
 #include "wimlib.h"
 #include "wimlib/assert.h"
-#include "wimlib/buffer_io.h"
+#include "wimlib/endianness.h"
 #include "wimlib/error.h"
 #include "wimlib/file_io.h"
 #include "wimlib/header.h"
 #include "wimlib/wim.h"
 
 #include <limits.h>
+#include <string.h>
+
+/* WIM magic characters, translated to a single 64-bit little endian number. */
+#define WIM_MAGIC \
+               cpu_to_le64(((u64)'M' << 0) |           \
+                           ((u64)'S' << 8) |           \
+                           ((u64)'W' << 16) |          \
+                           ((u64)'I' << 24) |          \
+                           ((u64)'M' << 32) |          \
+                           ((u64)'\0' << 40) |         \
+                           ((u64)'\0' << 48) |         \
+                           ((u64)'\0' << 54))
+
+/* On-disk format of the WIM header. */
+struct wim_header_disk {
+
+       /* Magic characters "MSWIM\0\0\0" */
+       le64 magic;
+
+       /* Size of the WIM header, in bytes; WIM_HEADER_DISK_SIZE expected
+        * (currently the only supported value). */
+       u32 hdr_size;
+
+       /* Version of the WIM file; WIM_VERSION expected (currently the only
+        * supported value). */
+       u32 wim_version;
+
+       /* Flags for the WIM file (WIM_HDR_FLAG_*) */
+       u32 wim_flags;
+
+       /* Uncompressed chunk size of resources in the WIM.  0 if the WIM is
+        * uncompressed.  If compressed, WIM_CHUNK_SIZE is expected (currently
+        * the only supported value).  */
+       u32 chunk_size;
+
+       /* Globally unique identifier for the WIM file.  Basically bunch of
+        * random bytes. */
+       u8 guid[WIM_GID_LEN];
+
+       /* Number of this WIM part in the split WIM file, indexed from 1, or 1
+        * if the WIM is not split. */
+       u16 part_number;
+
+       /* Total number of parts of the split WIM file, or 1 if the WIM is not
+        * split. */
+       u16 total_parts;
+
+       /* Number of images in the WIM. */
+       u32 image_count;
+
+       /* Location and size of the WIM's lookup table. */
+       struct resource_entry_disk lookup_table_res_entry;
+
+       /* Location and size of the WIM's XML data. */
+       struct resource_entry_disk xml_data_res_entry;
+
+       /* Location and size of metadata resource for the bootable image of the
+        * WIM, or all zeroes if no image is bootable. */
+       struct resource_entry_disk boot_metadata_res_entry;
+
+       /* 1-based index of the bootable image of the WIM, or 0 if no image is
+        * bootable. */
+       u32 boot_idx;
+
+       /* Location and size of the WIM's integrity table, or all zeroes if the
+        * WIM has no integrity table. */
+
+       /* Note the integrity_table_res_entry here is 4-byte aligned even though
+        * it would ordinarily be 8-byte aligned--- hence, the _packed_attribute
+        * on the `struct wim_header_disk' is essential. */
+       struct resource_entry_disk integrity_table_res_entry;
 
-/* First 8 bytes in every WIM file. */
-static const u8 wim_magic_chars[WIM_MAGIC_LEN] = {
-                       'M', 'S', 'W', 'I', 'M', '\0', '\0', '\0' };
+       /* Unused bytes. */
+       u8 unused[60];
+} _packed_attribute;
 
 /* Reads the header from a WIM file.  */
 int
 read_header(const tchar *filename, int in_fd,
            struct wim_header *hdr, int open_flags)
 {
-       size_t bytes_read;
-       u8 buf[WIM_HEADER_DISK_SIZE];
-       const void *p;
+       struct wim_header_disk disk_hdr _aligned_attribute(8);
 
-       u32 hdr_size;
-       u32 wim_version;
-       u32 chunk_size;
-
-       DEBUG("Reading WIM header from \"%"TS"\".", filename);
+       DEBUG("Reading WIM header from \"%"TS"\"", filename);
 
-       bytes_read = full_pread(in_fd, buf, WIM_HEADER_DISK_SIZE, 0);
-
-       if (bytes_read != WIM_HEADER_DISK_SIZE) {
+       if (full_pread(in_fd, &disk_hdr, sizeof(disk_hdr), 0) != sizeof(disk_hdr)) {
                ERROR_WITH_ERRNO("\"%"TS"\": Error reading header", filename);
                return WIMLIB_ERR_READ;
        }
 
-       p = buf;
-       if (memcmp(p, wim_magic_chars, WIM_MAGIC_LEN)) {
+       if (disk_hdr.magic != WIM_MAGIC) {
                ERROR("\"%"TS"\": Invalid magic characters in header", filename);
                return WIMLIB_ERR_NOT_A_WIM_FILE;
        }
 
-       /* Byte 8 */
-       p = get_u32(p + 8, &hdr_size);
-       if (hdr_size != WIM_HEADER_DISK_SIZE) {
-               ERROR("\"%"TS"\": Header is %u bytes (expected %u bytes)",
-                     filename, hdr_size, WIM_HEADER_DISK_SIZE);
+       BUILD_BUG_ON(sizeof(struct wim_header_disk) != WIM_HEADER_DISK_SIZE);
+       if (le32_to_cpu(disk_hdr.hdr_size) != sizeof(struct wim_header_disk)) {
+               ERROR("\"%"TS"\": Header size is invalid (%u bytes)",
+                     filename, le32_to_cpu(disk_hdr.hdr_size));
                return WIMLIB_ERR_INVALID_HEADER_SIZE;
        }
 
-       /* Byte 12 */
-       p = get_u32(buf + WIM_MAGIC_LEN + sizeof(u32), &wim_version);
-       if (wim_version != WIM_VERSION) {
+       if (le32_to_cpu(disk_hdr.wim_version) != WIM_VERSION) {
                ERROR("\"%"TS"\": The WIM header says the WIM version is %u, "
                      "but wimlib only knows about version %u",
-                     filename, wim_version, WIM_VERSION);
+                     filename, le32_to_cpu(disk_hdr.wim_version), WIM_VERSION);
                return WIMLIB_ERR_UNKNOWN_VERSION;
        }
 
-       p = get_u32(p, &hdr->flags);
-       p = get_u32(p, &chunk_size);
-       if (chunk_size != WIM_CHUNK_SIZE &&
+       hdr->flags = le32_to_cpu(disk_hdr.wim_flags);
+       if (le32_to_cpu(disk_hdr.chunk_size) != WIM_CHUNK_SIZE &&
            (hdr->flags & WIM_HDR_FLAG_COMPRESSION)) {
                ERROR("\"%"TS"\": Unexpected chunk size of %u! Ask the author to "
                      "implement support for other chunk sizes.",
-                     filename, chunk_size);
+                     filename, le32_to_cpu(disk_hdr.chunk_size));
                ERROR("(Or it might just be that the WIM header is invalid.)");
                return WIMLIB_ERR_INVALID_CHUNK_SIZE;
        }
 
-       p = get_bytes(p, WIM_GID_LEN, hdr->guid);
-       p = get_u16(p, &hdr->part_number);
-       p = get_u16(p, &hdr->total_parts);
+       memcpy(hdr->guid, disk_hdr.guid, WIM_GID_LEN);
+
+       hdr->part_number = le16_to_cpu(disk_hdr.part_number);
+       hdr->total_parts = le16_to_cpu(disk_hdr.total_parts);
 
-       if (hdr->total_parts == 0 ||
-           hdr->part_number == 0 ||
+       if (hdr->total_parts == 0 || hdr->part_number == 0 ||
            hdr->part_number > hdr->total_parts)
        {
                ERROR("\"%"TS"\": Invalid WIM part number: %hu of %hu",
@@ -111,15 +169,14 @@ read_header(const tchar *filename, int in_fd,
                return WIMLIB_ERR_INVALID_PART_NUMBER;
        }
 
-       if (!(open_flags & WIMLIB_OPEN_FLAG_SPLIT_OK) &&
-           hdr->total_parts != 1)
+       if (!(open_flags & WIMLIB_OPEN_FLAG_SPLIT_OK) && hdr->total_parts != 1)
        {
                ERROR("\"%"TS"\": This WIM is part %u of a %u-part WIM",
                      filename, hdr->part_number, hdr->total_parts);
                return WIMLIB_ERR_SPLIT_UNSUPPORTED;
        }
 
-       p = get_u32(p, &hdr->image_count);
+       hdr->image_count = le32_to_cpu(disk_hdr.image_count);
 
        DEBUG("part_number = %u, total_parts = %u, image_count = %u",
              hdr->part_number, hdr->total_parts, hdr->image_count);
@@ -130,26 +187,11 @@ read_header(const tchar *filename, int in_fd,
                return WIMLIB_ERR_IMAGE_COUNT;
        }
 
-       /* Byte 48 */
-
-       p = get_resource_entry(p, &hdr->lookup_table_res_entry);
-       p = get_resource_entry(p, &hdr->xml_res_entry);
-       p = get_resource_entry(p, &hdr->boot_metadata_res_entry);
-
-       /* Byte 120 */
-
-       p = get_u32(p, &hdr->boot_idx);
-
-       /* Byte 124 */
-
-       p = get_resource_entry(p, &hdr->integrity);
-
-       /* Byte 148 */
-
-       /* 60 bytes of unused stuff. */
-
-       /* Byte 208 */
-
+       get_resource_entry(&disk_hdr.lookup_table_res_entry, &hdr->lookup_table_res_entry);
+       get_resource_entry(&disk_hdr.xml_data_res_entry, &hdr->xml_res_entry);
+       get_resource_entry(&disk_hdr.boot_metadata_res_entry, &hdr->boot_metadata_res_entry);
+       hdr->boot_idx = le32_to_cpu(disk_hdr.boot_idx);
+       get_resource_entry(&disk_hdr.integrity_table_res_entry, &hdr->integrity);
        return 0;
 }
 
@@ -164,34 +206,28 @@ read_header(const tchar *filename, int in_fd,
 int
 write_header(const struct wim_header *hdr, int out_fd)
 {
-       u8 buf[WIM_HEADER_DISK_SIZE];
-       u8 *p;
+       struct wim_header_disk disk_hdr _aligned_attribute(8);
        DEBUG("Writing WIM header.");
 
-       p = put_bytes(buf, WIM_MAGIC_LEN, wim_magic_chars);
-       p = put_u32(p, WIM_HEADER_DISK_SIZE);
-       p = put_u32(p, WIM_VERSION);
-       p = put_u32(p, hdr->flags);
-       p = put_u32(p, (hdr->flags & WIM_HDR_FLAG_COMPRESSION) ?
-                               WIM_CHUNK_SIZE : 0);
-       /* Byte 24 */
-
-       p = put_bytes(p, WIM_GID_LEN, hdr->guid);
-       p = put_u16(p, hdr->part_number);
-
-       /* Byte 40 */
-
-       p = put_u16(p, hdr->total_parts);
-       p = put_u32(p, hdr->image_count);
-       p = put_resource_entry(p, &hdr->lookup_table_res_entry);
-       p = put_resource_entry(p, &hdr->xml_res_entry);
-       p = put_resource_entry(p, &hdr->boot_metadata_res_entry);
-       p = put_u32(p, hdr->boot_idx);
-       p = put_resource_entry(p, &hdr->integrity);
-       p = put_zeroes(p, WIM_UNUSED_LEN);
-       wimlib_assert(p - buf == sizeof(buf));
-
-       if (full_pwrite(out_fd, buf, sizeof(buf), 0) != sizeof(buf)) {
+       disk_hdr.magic = WIM_MAGIC;
+       disk_hdr.hdr_size = cpu_to_le32(sizeof(struct wim_header_disk));
+       disk_hdr.wim_version = cpu_to_le32(WIM_VERSION);
+       disk_hdr.wim_flags = cpu_to_le32(hdr->flags);
+       disk_hdr.chunk_size = cpu_to_le32((hdr->flags & WIM_HDR_FLAG_COMPRESSION) ?
+                                               WIM_CHUNK_SIZE : 0);
+       memcpy(disk_hdr.guid, hdr->guid, WIM_GID_LEN);
+
+       disk_hdr.part_number = cpu_to_le16(hdr->part_number);
+       disk_hdr.total_parts = cpu_to_le16(hdr->total_parts);
+       disk_hdr.image_count = cpu_to_le32(hdr->image_count);
+       put_resource_entry(&hdr->lookup_table_res_entry, &disk_hdr.lookup_table_res_entry);
+       put_resource_entry(&hdr->xml_res_entry, &disk_hdr.xml_data_res_entry);
+       put_resource_entry(&hdr->boot_metadata_res_entry, &disk_hdr.boot_metadata_res_entry);
+       disk_hdr.boot_idx = cpu_to_le32(hdr->boot_idx);
+       put_resource_entry(&hdr->integrity, &disk_hdr.integrity_table_res_entry);
+       memset(disk_hdr.unused, 0, sizeof(disk_hdr.unused));
+
+       if (full_pwrite(out_fd, &disk_hdr, sizeof(disk_hdr), 0) != sizeof(disk_hdr)) {
                ERROR_WITH_ERRNO("Failed to write WIM header");
                return WIMLIB_ERR_WRITE;
        }