Fix filesystem read issues, load/save rom demo is working

1 files changed, 27 insertions, 6 deletions

diff --git a/src/filesystem.c b/src/filesystem.c
index 1521d69..69e23f7 100644
--- a/src/filesystem.c
+++ b/src/filesystem.c
@@ -47,6 +47,12 @@ fs_init() {
     if (filesystem.num_files == 0xFFFF
             && filesystem.data_capacity == 0xFFFF
             && filesystem.data_size == 0xFFFF) {
+        // Clear SRAM.
+        for (size_t i = 0; i < KB(64); ++i) {
+            SRAM[i] = 0;
+        }
+
+        // Initialize filesystem.
         filesystem.num_files = 0;
         filesystem.data_size = 0;
         filesystem.data_capacity = 27 * FILE_MAX_SIZE;
@@ -57,8 +63,13 @@ fs_init() {
     }
 }
 
+typedef enum {
+    OPEN_READ,
+    OPEN_WRITE,
+} OpenMode;
+
 int
-fs_open_file(char *name) {
+fs_open_file(char *name, OpenMode mode) {
     // Try to find an existing file.
     for (size_t i = 0; i < filesystem.num_files; ++i) {
         // TODO: Replace strcmp with vectorized fixed size char comparison.
@@ -66,6 +77,11 @@ fs_open_file(char *name) {
             return i;
         }
     }
+
+    if (mode == OPEN_READ) {
+        return -1;
+    }
+
     // Create a new file if there is space.
     if (filesystem.num_files < FILE_CAPACITY) {
         size_t index = filesystem.num_files++;
@@ -89,13 +105,13 @@ fs_open_file(char *name) {
     return -1;
 }
 
-int
+size_t
 fs_write(u8 *src, size_t n_bytes, u16 file_index, u16 offset, bool append) {
     File *file = &filesystem.files[file_index];
 
     // Check if there is enough capacity for this write operation.
     if (offset + n_bytes >= FILE_MAX_SIZE) {
-        return -1;
+        return 0;
     }
 
     // Write data to file block.
@@ -117,13 +133,18 @@ fs_write(u8 *src, size_t n_bytes, u16 file_index, u16 offset, bool append) {
     return n_bytes;
 }
 
-int
+size_t
 fs_read(u8 *dst, size_t n_bytes, u16 file_index, u16 offset) {
     File *file = &filesystem.files[file_index];
 
     // Check if the offset is within limits.
-    if (offset + n_bytes >= FILE_MAX_SIZE) {
-        return -1;
+    if (file->size == 0 || offset >= file->size - 1) {
+        return 0;
+    }
+
+    // Read as much as we can.
+    if (offset + n_bytes > file->size) {
+        n_bytes = file->size - offset;
     }
 
     // Copy n_bytes to destination.