Implement OS read command for Linux.

linux/device.c

@@ -343,4 +343,24 @@ int32_t ReOpen(void* device_ctx, uint32_t* closeFailed)
     if((ctx->fd < 0) && (errno == EACCES || errno == EROFS)) ctx->fd = open(ctx->device_path, O_RDONLY | O_NONBLOCK);
 
     return ctx->fd <= 0 ? errno : 0;
+}
+
+int32_t OsRead(void* device_ctx, char* buffer, uint64_t offset, uint32_t length, uint32_t* duration)
+{
+    DeviceContext* ctx = device_ctx;
+    ssize_t        ret;
+    *duration = 0;
+    off_t pos;
+
+    if(!ctx) return -1;
+
+    // TODO: Timing
+    pos = lseek(ctx->fd, (off_t)offset, SEEK_SET);
+
+    if(pos < 0) return errno;
+
+    // TODO: Timing
+    ret = read(ctx->fd, (void*)buffer, (size_t)length);
+
+    return ret < 0 ? errno : 0;
 }