Implementing patch algorithm

Makefile

@@ -1,6 +1,6 @@
 TARGET = umd_livepatch
 C_OBJS = patch.o io_funcs.o main.o \
-		 stdio_glue.o umdiff/file.o
+		 stdio_glue.o umdiff/file.o umdiff/patch.o
 OBJS = $(C_OBJS) imports.o
 all: $(TARGET).prx
 INCDIR = $(ARKROOT)/common/include $(ARKROOT)/core/systemctrl/include $(LIBRSYNC)/src

umdiff/Makefile

@@ -1,5 +1,5 @@
 TARGET = umdiff
-C_OBJS = main.c.o compare.c.o file.c.o patch.c.o
+C_OBJS = main.c.o rdiff.c.o compare.c.o file.c.o patch.c.o
 OBJS   = $(C_OBJS)
 
 CMAKE := cmake

umdiff/file.c

@@ -6,6 +6,8 @@
  *
  * The functions defined here control reading and writing UMDiff files from
  * in-memory structure @ref umdiff_File.
+ *
+ * @warning This file is reused by umd_livepatch. Do not allocate on the heap!
  */
 
 #include "umdiff.h"
@@ -28,7 +30,7 @@ _impl_umdiff_Header_rectify(umdiff_Header *hdr)
     long len_preamble = sizeof(umdiff_Header)
                       + (sizeof(umdiff_Command) * hdr->cmd_count);
 
-    strncpy(hdr->magic, umdiff_File_$MAGIC, 7);
+    memcpy(hdr->magic, umdiff_File_$MAGIC, 7);
     hdr->version = umdiff_File_$VERSION;
     hdr->data_start = _impl_umdiff_alignSector$(len_preamble);
 }

umdiff/patch.c

@@ -0,0 +1,82 @@
+/**
+ * @file       patch.c
+ * @author     Karim Vergnes <me@thesola.io>
+ * @copyright  GPLv2
+ * @brief      UMDiff patch algorithms
+ *
+ * Functions to redirect read requests and reconstruct the result file given
+ * a set of UMDiff commands.
+ *
+ * @warning This file is reused by umd_livepatch. Do not allocate on the heap!
+ */
+
+#include "umdiff.h"
+
+static long
+_impl_umdiff_Command_read(umdiff_Command cmd, void *dest, long count, long offset,
+                          umdiff_ReadCallback read_source,
+                          umdiff_ReadCallback read_patchFile)
+{
+    long rel_offset = offset - (cmd.sector_start * ISO_SECTOR_SIZE);
+
+    //TODO: implement read system
+    // 1. perform first truncated read
+    // 2. if repeat-length remains, perform second full read
+    // 3. if repeat-length still remains, memcpy second read range onwards
+    //    -> saved a bunch of i/o calls at the guest ptr's expense!
+}
+
+static umdiff_Command *
+_impl_umdiff_File_readIndexCmds(umdiff_File *file, long offset_sector,
+                                umdiff_ReadCallback read_patchFile)
+{
+    int res;
+    int index = offset_sector / 1024;
+
+    // stateful optimization: don't re-read the same commands
+    if (index == file->last_index)
+        return 0;
+
+    if (file->mode == umdiff_FileFlags_HEADER_ONLY) {
+        res = read_patchFile(file->commands, sizeof(umdiff_Command) * 1024,
+                             file->hdr.index[index]);
+        return file->commands;
+    } else {
+        return file->commands + file->hdr.index[index] - umdiff_File_$COMMANDS_START;
+    }
+
+    file->last_index = index;
+}
+
+int
+umdiff_File_readPatched(umdiff_File *file, void *dest, long count, long offset,
+                        umdiff_ReadCallback read_source,
+                        umdiff_ReadCallback read_patchFile)
+{
+    long res;
+    umdiff_Command *commands;
+    umdiff_Command *curCommand;
+
+#define $offset_sectors (offset / ISO_SECTOR_SIZE)
+
+    while (count > 0) {
+        commands = _impl_umdiff_File_readIndexCmds(file, $offset_sectors,
+                                                   read_patchFile);
+        curCommand = 0;
+
+        for (int i = 0; i < 1024; i++) {
+            if (commands[i].sector_start <= $offset_sectors) {
+                curCommand = &commands[i];
+                break;
+            }
+        }
+        res = _impl_umdiff_Command_read(*curCommand, dest, count, offset,
+                                        read_source, read_patchFile);
+        dest += res;
+        count -= res;
+    }
+
+    return res;
+}
+
+// vim: ft=c.doxygen

umdiff/rdiff.c

@@ -0,0 +1,15 @@
+/**
+ * @file       rdiff.c
+ * @author     Karim Vergnes <me@thesola.io>
+ * @copyright  GPLv2
+ * @brief      rsync diff parser
+ *
+ * This file parses and converts rdiff commands into equivalent UMDiff commands
+ * and manages the corresponding data bucket.
+ */
+
+#include <prototab.h>
+
+
+
+// vim: ft=c.doxygen

umdiff/umdiff.h

@@ -18,7 +18,7 @@
 #define umdiff_File_$VERSION 0x00
 
 // Commands shall start immediately after the full header
-#define umdiff_File_$COMMANDS_START (sizeof lp_UMDiffHeader)
+#define umdiff_File_$COMMANDS_START (sizeof(umdiff_Header))
 
 /**
  * @brief      Index of commands at 1024 sector interval.
@@ -101,16 +101,40 @@ typedef enum {
  * This struct represents the contents of a UMDiff file, loaded in memory.
  * If read from a file, only the header is guaranteed to be populated.
  *
+ * If <tt>commands</tt> is set to point to a 1024-command buffer, and <tt>mode</tt>
+ * is set to @ref umdiff_FileFlags_HEADER_ONLY, it will be used as a holding
+ * buffer when reading commands from file.
+ *
  * @see umdiff_FileFlags for the possible cases.
  */
 typedef struct {
     umdiff_Header hdr;
+
+    /**
+     * @brief List of loaded commands from file
+     *
+     * If <tt>mode</tt> is set to @ref umdiff_FileFlags_HEADER_ONLY, this is
+     * expected to be a pre-allocated buffer holding 1024 commands.
+     * Otherwise, it contains all commands in the file.
+     */
     umdiff_Command *commands;
-    long data_len;
     char *data;
+    long data_len;
+
+    /** Keeps track of the last command batch pulled from index. */
+    int last_index;
+    /** Which loading mode was used when this file was opened. */
     umdiff_FileFlags mode;
 } umdiff_File;
 
+/**
+ * @brief      Callback function to read from a source.
+ *
+ * This is used by @ref umdiff_File_readPatched to perform an actual read from
+ * a data source, be it the patch file or original media.
+ */
+typedef int (*umdiff_ReadCallback)(void *dest, long count, long offset);
+
 /**
  * @brief      Load a UMDiff file from an open file descriptor.
  *
@@ -141,6 +165,25 @@ umdiff_File_load(umdiff_File *file, int fd, umdiff_FileFlags flags);
 int
 umdiff_File_write(umdiff_File *file, int outfd);
 
+/**
+ * @brief      Perform a read at a given offset and size with patches applied.
+ *
+ * This function maps a given read request into the patched data, using the
+ * provided callback functions to carry out the actual read commands needed.
+ *
+ * @param file             The @ref umdiff_File to perform the patch with.
+ * @param dest             Like pread(2), the buffer to write the data into.
+ * @param count            Like pread(2), the amount of data to read.
+ * @param offset           Like pread(2), the offset at which to start reading.
+ *
+ * @param read_source      The function to read the source media.
+ * @param read_patchFile   The function to read the patch file from storage.
+ */
+int
+umdiff_File_readPatched(umdiff_File *file, void *dest, long count, long offset,
+                        umdiff_ReadCallback read_source,
+                        umdiff_ReadCallback read_patchFile);
+
 #endif //__UMDIFF_H
 
 // vim: ft=c.doxygen