add initial tests for DOS absolute sector read/write

tests/absread/absread.c

@@ -0,0 +1,208 @@
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+typedef unsigned long uint32_t;
+typedef unsigned short uint16_t;
+typedef unsigned char uint8_t;
+
+void die(char *msg)
+{
+  printf("%s\n", msg);
+  exit(1);
+}
+
+/* Both traditional DOS and FAT32 DOS return this structure, but
+   FAT32 return a lot more data, so make sure we have plenty of space */
+struct deviceparams {
+    uint8_t specfunc;
+    uint8_t devtype;
+    uint16_t devattr;
+    uint16_t cylinders;
+    uint8_t mediatype;
+    uint16_t bytespersec;
+    uint8_t secperclust;
+    uint16_t ressectors;
+    uint8_t fats;
+    uint16_t rootdirents;
+    uint16_t sectors;
+    uint8_t media;
+    uint16_t fatsecs;
+    uint16_t secpertrack;
+    uint16_t heads;
+    uint32_t hiddensecs;
+    uint32_t hugesectors;
+    uint8_t lotsofpadding[224];
+};
+
+void get_partition_offset(int drive)
+{
+    static struct deviceparams dp;
+    int err=0;
+    
+    printf("Getting drive info: int21h function 440Dh subfunction 0860h\n");
+    
+    dp.specfunc = 1;		/* Get current information */
+
+    __asm {
+      mov ax, 0x440d
+      mov bx, drive
+      mov cx, 0x0860
+      mov dx, offset dp
+      int 0x21
+      mov ax, 0
+      adc ax, 0
+      mov err, ax
+    }
+
+    if (!err)
+    {
+      printf("Partition Offset = %02lXh  [c=%02u,h=%02u,s=%2u]\n",  dp.hiddensecs, dp.cylinders, dp.heads, dp.secpertrack);
+      printf("FAT32 version 4860h to compare\n"); 
+    }
+    else
+      printf("Original version failed, checking FAT32 version using 4860h\n");
+     
+    __asm {
+      mov ax, 0x440d
+      mov bx, drive
+      mov cx, 0x4860
+      mov dx, offset dp
+      int 0x21
+      mov ax, 0
+      adc ax, 0
+      mov err, ax
+    }
+
+    if (!err)
+    {
+      printf("Partition Offset = %02lXh\n",  dp.hiddensecs);
+      return;
+    }
+    else
+      printf("FAT32 version failed.\n");
+}
+
+struct rwblock {
+    uint8_t special;
+    uint16_t head;
+    uint16_t cylinder;
+    uint16_t firstsector;
+    uint16_t sectors;
+    uint16_t bufferoffset;
+    uint16_t bufferseg;
+};
+
+static struct rwblock mbr = {
+    .special = 0,
+    .head = 0,
+    .cylinder = 0, /* 5265, 3fh */
+    .firstsector = 0,		/* MS-DOS, unlike the BIOS, zero-base sectors */
+    .sectors = 1,
+    .bufferoffset = 0,
+    .bufferseg = 0
+};
+
+
+void read_mbr(int drive, const void *buf)
+{
+    uint8_t err=0;
+    uint16_t ds_seg=0;
+
+    //printf("read_mbr(%c:,%p)", 'a'+drive-1, buf);
+
+    mbr.bufferoffset = (unsigned short)buf;
+    __asm {
+      push ds
+      pop ax
+      mov ds_seg, ax
+    }
+    mbr.bufferseg = ds_seg;
+    //printf("DS = %04Xh\n", ds_seg);
+
+    __asm {
+      mov ax, 0x440d
+      mov bx, drive
+      mov cx, 0x0861
+      mov dx, offset mbr
+      int 0x21
+      mov ax, 0
+      adc ax, 0
+      mov err, al
+    }
+
+    if (!err) {
+      //printf("Success reading MBR\n\n");
+      return;
+    }
+    
+    __asm {
+      mov ax, 0x440d
+      mov bx, drive
+      mov cx, 0x4861
+      mov dx, offset mbr
+      int 0x21
+      mov ax, 0
+      adc ax, 0
+      mov err, al
+    }
+
+    if (!err) {
+      //printf("Success reading FAT32 MBR\n\n");
+      return;
+    }
+    
+    printf("mbr read error");
+}
+
+int main(int argc, char *argv[]) 
+{
+    unsigned int c,h,s;
+    static uint8_t buf[1024];
+    unsigned drive = (unsigned)(argv[1][0]);  /* a=1,b=2,... */
+    drive = drive-'a'+1;
+    printf("Query drive %c:\n", 'a'+drive-1);
+    
+    get_partition_offset(drive);
+    
+    read_mbr(drive, buf);
+    printf("MBR: %02Xh %02Xh %02Xh %02Xh %02Xh %02Xh %02Xh %02Xh\n",
+	    ((const uint8_t *)buf)[0],
+	    ((const uint8_t *)buf)[1],
+	    ((const uint8_t *)buf)[2],
+	    ((const uint8_t *)buf)[3],
+	    ((const uint8_t *)buf)[4],
+	    ((const uint8_t *)buf)[5],
+	    ((const uint8_t *)buf)[6],
+	    ((const uint8_t *)buf)[7]);
+
+    printf("Finding drive\n");
+    for (c = 1024; c <= 5265; c++) {
+    for (h = 0; h < 255; h++)
+    for (s = 0; s <= 63; s++)
+    {
+      mbr.cylinder = c;
+      mbr.head =h;
+      mbr.sectors=s;
+      read_mbr(drive, buf);
+      if (buf[0] != 0) {
+          printf("Found at %u,%u,%u\n", c,h,s); 
+
+          printf("MBR: %02Xh %02Xh %02Xh %02Xh %02Xh %02Xh %02Xh %02Xh\n",
+	    ((const uint8_t *)buf)[0],
+	    ((const uint8_t *)buf)[1],
+	    ((const uint8_t *)buf)[2],
+	    ((const uint8_t *)buf)[3],
+	    ((const uint8_t *)buf)[4],
+	    ((const uint8_t *)buf)[5],
+	    ((const uint8_t *)buf)[6],
+	    ((const uint8_t *)buf)[7]);
+          
+          exit(0);
+      }
+    }
+    printf("c=%u,", c); fflush(NULL);
+    }
+      
+    return 0;
+}

tests/absread/build.bat

@@ -0,0 +1,2 @@
+@ECHO OFF
+wcl -e3-we-wx-zq-os-s-zp1-mt-bt=DOS absread.c