Merge pull request #11 from Sani7/feature/llfs-extended-fs-api

Extended the llfs file system api

docs/llfs.md

@@ -1,17 +1,52 @@
 # LLFS (Linked List File System)
 
 ## Introduction
-The llfs filesystem can be generated using the mkllfss utility. 
+The llfs filesystem can be generated using the [mkllfs](mkllfs.md) utility.
-It is a simple filesystem that uses a linked list to store files. 
+The resulting C file encapsulates the filesystem data within a linked list which can be used by the llfs library.
-The filesystem is stored in a single c file (`llfs_data.c`), which can be compiled and read by the llfs library.
+
-The llfs filesystem is a flat filesystem, meaning that it does not support directories.
+As a flat filesystem, llfs lacks support for directories. 
+Using the llfs API, information about the files in the filesystem can be retrieved,
+and the files can be read using direct memory access.
+Alternatively, the POSIX file functions can be used. 
+But this is more resource intensive, as data must be copied before using it.
+
+It's essential to note that the llfs filesystem operates in a read-only mode,
+restricting operations solely to read functions.
+
+## Table of contents
+ - [Introduction](#introduction)
+ - [Table of contents](#table-of-contents)
+ - [Initialization](#initialization)
+ - [Usage of the llfs API](#usage-of-the-llfs-api)
+   - [The `llfs_file_t` struct](#the-llfs_file_t-struct)
+   - [Getting a list of files](#getting-a-list-of-files)
+     - [Iterator function (not recommended)](#iterator-function-not-recommended)
+   - [Reading a file](#reading-a-file)
+   - [Getting the number of files](#getting-the-number-of-files)
+ - [Using the POSIX file functions](#using-the-posix-file-functions)
+
+## Initialization
+Before using the llfs API, or the file related POSIX (fopen, fgetc, ...) functions, the filesystem must be initialized by calling `llfs_init()`.
 
 ## Usage of the llfs API
+### The `llfs_file_t` struct
+The `llfs_file_t` struct contains information about a file in the filesystem.
+```c
+typedef struct {
+    const uint8_t* data; // Pointer to the file data (len bytes)
+    const char* name;    // Null-terminated string with the filename
+    size_t len;          // Length of the file data
+} llfs_file_t;
+```
+The data pointer points to the data of the file in the filesystem, and can be used to read the file.
+
 ### Getting a list of files
 ```c
 #include "llfs.h"
 
 void main(void) {
+    llfs_init();
+    
     // Allocate space for 10 files
     llfs_file_t file_list[10];
     
@@ -33,11 +68,48 @@ Result:
 [Info]      (2031) [main]: File: file1.txt, size: 77
 ```
 
+It is also possible to use a file extension filter (e.g. `*.bmp`, `*.txt`, `*.py`).
+```c
+    // ...
+    size_t file_count = llfs_file_list(file_list, 10, "*.bmp");
+    // ...
+```
+This will only return files with the `.bmp` extension.
+````
+[Info]      (2009) [main]: File: image.bmp, size: 9270
+[Info]      (2019) [main]: File: image2.bmp, size: 7738
+````
+
+#### Iterator function (not recommended)
+It is also possible to iterate through the files without allocating an array.
+When the memory pointer is `NULL`, the iterator will start at the beginning of the file list. 
+Each call to `llfs_next_file()` will return the next file in the list,
+if a filter is specified files that don't match the filter will be skipped.
+```c
+#include "llfs.h"
+
+void main(void) {
+    llfs_init();
+    
+    // Get the file list
+    void* mem = NULL;   // Pointer for internal use by the llfs library
+    llfs_file_t* file;
+    while ((file = llfs_next_file(&mem, ".bmp")) != NULL) {
+        LOG_INFO(TAG, "File: %s", file->name);
+    }
+}
+```
+While this method doesn't require allocating memory for the file list,
+it is slower than the previous method due to the overhead calling the function for each file.
+Additionally, the required memory for the filelist is very small, so it's recommended to use the first method. 
+
 ### Reading a file
 ```c
 #include "llfs.h"
 
 void main(void) {
+    llfs_init();
+    
     // Get a file by name
     llfs_file_t* file = llfs_file_open("filename with a space.txt");
     
@@ -55,3 +127,37 @@ Result:
 [Info]      (2040) [main]: File found: filename with a space.txt, size: 61
 [Info]      (2047) [main]: File data: This is a file with a space in it's filename.
 ```
+
+### Getting the number of files
+```c
+#include "llfs.h"
+
+void main(void) {
+    llfs_init();
+    
+    // Get the number of files
+    size_t file_count = llfs_file_count();
+    
+    // Print the number of files
+    LOG_INFO(TAG, "File count: %d", file_count);
+}
+```
+
+## Using the POSIX file functions
+The llfs library also supports the POSIX file functions.
+As the file system is read-only, write functions are not implemented.
+There is also a limit on the number of files that can be open concurrently,
+this is set by the `POSIX_MAX_FILES` macro in `llfs.c`. 
+The default value is 10, but there are already 3 files in use (stdin, stdout, stderr),
+so the maximum number of files that can be open is 7.
+
+The following functions are tested and working, but other functions might also work:
+ - `fopen`
+ - `fclose`
+ - `fgetc`
+ - `fread`
+ - `fseek`
+ - `ftell`
+ - `rewind`
+ - `fstat`
+ - `fileno`

project/Core/Inc/llfs.h

@@ -2,6 +2,7 @@
  * @file llfs.h
  * @brief Linked List Filesystem header (llfs)
  * @author Lorenz C.
+ * @version 0.1.1
  */
 
 #ifndef LLFS_H
@@ -30,20 +31,25 @@ struct llfs_data_file {
     const struct llfs_data_file* next;
 };
 
+/**
+ * @brief Initialize the llfs filesystem
+ * @note This function should be called before any other llfs function or POSIX file operation (e.g. fopen, fread, ...)
+ * @return 0 on success
+ */
+int8_t llfs_init(void);
+
 /**
  * @brief Get a list of files in the filesystem
  * Get a list of all the files in the filesystem.
  *
- * Use the filter to filter out files with a filename that do not match the filter. (e.g. "*.txt" or "*.png|*.jpg") (not
+ * Use the filter to filter out files with a filename that do not match the file extension filter.
- * implemented yet) Multiple filters can be used by separating them with a pipe (|).
  *
  * The following members of the llfs_file_t struct are set: name, len and data. @ref llfs_file_t
  *
- * @todo Implement file filter
  *
  * @param[out] file_list A pointer to an array of llfs_file_t to store the files in @ref llfs_file_t
  * @param[in] max_files The maximum number of files to return (size of file_list)
- * @param[in] filter A string with file extensions to filter out. (e.g. "*.txt" or "*.png|*.jpg")
+ * @param[in] filter A string with the file extensions to filter out. (e.g. "*.txt" or "*.png")
  * @return The number of files returned
  */
 size_t llfs_file_list(llfs_file_t* file_list, size_t max_files, char* filter);
@@ -58,4 +64,23 @@ size_t llfs_file_list(llfs_file_t* file_list, size_t max_files, char* filter);
  */
 llfs_file_t* llfs_file_open(const char* name);
 
+/**
+ * @brief Iterate over all files in the filesystem
+ * For each call (with the same mem pointer) the next file in the filesystem is returned.
+ * The first call should be with mem = NULL.
+ * If a filter is specified, only files with a filename that matches the filter are returned.
+ *
+ * @param[in, out] mem A pointer to a void* that is used internally to keep track of the current file
+ * @param[in] filter  A string with file extension to filter out. (e.g. "*.txt" or "*.png")
+ * @return The next file in the filesystem or NULL if there are no more files @ref llfs_file_t
+ */
+llfs_file_t* llfs_next_file(void** mem, char* filter);
+
+/**
+ * @brief Get the number of files in the filesystem
+ *
+ * @return The number of files in the filesystem
+ */
+size_t llfs_file_count(void);
+
 #endif // LLFS_H

project/Core/Src/llfs.c

@@ -2,34 +2,82 @@
  * @file llfs.c
  * @brief Linked List Filesystem implementation (llfs)
  * @author Lorenz C.
- * @todo Implement file extension filter
+ * @version 0.1.1
  */
 
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
 #include <string.h>
 #define LOGGER_LEVEL_WARN
 #include "llfs.h"
 #include "log.h"
 
+/**
+ * @brief The maximum number of files that can be opened concurrently using the POSIX API
+ */
+#define POSIX_MAX_FILES 10
+
 extern struct llfs_data_file* llfs_root;
 const char* TAG = "llfs";
-
-// TODO: Implement file extension filter
-size_t llfs_file_list(llfs_file_t* file_list, size_t max_files, char* filter) {
 size_t file_count = 0;
-    const struct llfs_data_file* file = llfs_root;
+FILE* file_table[POSIX_MAX_FILES];
 
-    LOG_DEBUG(TAG, "Getting file list with filter: %s", filter);
+static int new_file_table_entry(void);
+static int free_file_table_entry(int file_id);
+static FILE* file_id_to_stream(int file_id);
+static uint8_t file_ext_cmp(const char* filename, const char* ext);
 
+int8_t llfs_init(void) {
+    LOG_DEBUG(TAG, "Initializing llfs");
+
+    // Initialize the file table
+    for (int i = 0; i < POSIX_MAX_FILES; i++) {
+        file_table[i] = NULL;
+    }
+
+    // Add stdin, stdout and stderr to the file table
+    file_table[STDIN_FILENO] = stdin;
+    file_table[STDOUT_FILENO] = stdout;
+    file_table[STDERR_FILENO] = stderr;
+
+    return 0;
+}
+
+size_t llfs_file_list(llfs_file_t* file_list, size_t max_files, char* filter) {
+    size_t count = 0;                              // Number of files found
+    const struct llfs_data_file* file = llfs_root; // Pointer to the current file
+
+    if (filter != NULL) {
+        LOG_DEBUG(TAG, "Filtering files with filter: %s", filter);
+
+        if (filter[0] == '*') {
+            filter++;
+        }
+    }
+
+    // Iterate over all files in the filesystem
     while (file != NULL && file_count < max_files) {
-        file_list[file_count].data = file->data;
+        // Filter out files with a filename that does not match the filter
-        file_list[file_count].name = file->name;
+        if (filter != NULL) {
-        file_list[file_count].len = file->len;
+            if (!file_ext_cmp(file->name, filter)) {
-        file_count++;
+                file = file->next;
+                continue;
+            }
+        }
+
+        // Add the file to the file list
+        file_list[count].data = file->data;
+        file_list[count].name = file->name;
+        file_list[count].len = file->len;
+
+        // Move to the next file
+        count++;
         file = file->next;
     }
 
-    LOG_DEBUG(TAG, "Files found: %d", file_count);
+    LOG_DEBUG(TAG, "Files found: %d", count);
-    return file_count;
+    return count;
 }
 
 llfs_file_t* llfs_file_open(const char* name) {
@@ -48,3 +96,341 @@ llfs_file_t* llfs_file_open(const char* name) {
     LOG_DEBUG(TAG, "File not found: %s", name);
     return NULL;
 }
+
+llfs_file_t* llfs_next_file(void** mem, char* filter) {
+    struct llfs_data_file* prev_file = (struct llfs_data_file*)*mem;
+    uint8_t filter_ok = 0;
+
+    if (prev_file == NULL) {
+        prev_file = llfs_root;
+    } else {
+        prev_file = (struct llfs_data_file*)prev_file->next;
+    }
+
+    // If a filter is specified, only return files that match the filter
+    if (filter != NULL) {
+        LOG_DEBUG(TAG, "Filtering files with filter: %s", filter);
+
+        // Remove the '*' from the filter
+        if (filter[0] == '*') {
+            filter++;
+        }
+
+        while (prev_file != NULL) {
+            if (file_ext_cmp(prev_file->name, filter)) {
+                filter_ok = 1;
+                break;
+            }
+            prev_file = (struct llfs_data_file*)prev_file->next;
+        }
+    }
+
+    *mem = (void*)prev_file;
+    return (llfs_file_t*)prev_file;
+}
+
+size_t llfs_file_count(void) {
+    if (file_count == 0) {
+        const struct llfs_data_file* file = llfs_root;
+        while (file != NULL) {
+            file_count++;
+            file = file->next;
+        }
+    }
+    return file_count;
+}
+
+/**
+ * @brief Newlib open implementation
+ *
+ * @param path
+ * @param flags
+ * @param mode
+ * @return
+ */
+int _open(char* path, int flags, int mode) {
+    int file_id;
+    FILE* stream;
+    errno = 0;
+    llfs_file_t* llfs_file;
+
+    // Add a new entry to the file table
+    file_id = new_file_table_entry();
+    if (file_id < 0) {
+        LOG_WARN(TAG, "Failed to add new file table entry. %s", strerror(errno));
+        return -1;
+    }
+
+    // Get the stream associated with the file id
+    stream = file_id_to_stream(file_id);
+    if (stream == NULL) {
+        LOG_WARN(TAG, "Failed to get file table entry. %s", strerror(errno));
+        free_file_table_entry(file_id);
+        return -1;
+    }
+
+    // Get the file from the llfs filesystem
+    llfs_file = llfs_file_open(path);
+    if (llfs_file == NULL) {
+        LOG_DEBUG(TAG, "Failed to open file: %s", path);
+        free_file_table_entry(file_id);
+        return -1;
+    }
+
+    // Initialize the stream
+    stream->_cookie = (void*)llfs_file;
+    stream->_offset = 0;
+    stream->_flags = __SRD;
+
+    return file_id;
+}
+
+/**
+ * @brief Newlib close implementation
+ *
+ * @param file_id
+ * @return
+ */
+int _close(int file_id) {
+    FILE* stream;
+
+    // Get the stream associated with the file id
+    stream = file_id_to_stream(file_id);
+    if (stream == NULL) {
+        LOG_WARN(TAG, "Failed to get file table entry. %s", strerror(errno));
+        return -1;
+    }
+
+    // Remove the entry from the file table
+    if (free_file_table_entry(file_id) < 0) {
+        LOG_WARN(TAG, "Failed to remove file table entry. %s", strerror(errno));
+        return -1;
+    }
+
+    return 0;
+}
+
+/**
+ * @brief Newlib read implementation
+ *
+ * @param file_id
+ * @param ptr
+ * @param len
+ * @return
+ */
+int _read(int file_id, char* ptr, int len) {
+    FILE* stream;
+    llfs_file_t* llfs_file;
+    size_t bytes_read;
+
+    // Read from stdin, stdout and stderr is not supported
+    if (file_id == STDIN_FILENO || file_id == STDOUT_FILENO || file_id == STDERR_FILENO) {
+        LOG_DEBUG(TAG, "Trying to read from stdin, stdout or stderr: %d", file_id);
+        return -1;
+    }
+
+    // Get the stream associated with the file id
+    stream = file_id_to_stream(file_id);
+    if (stream == NULL) {
+        LOG_WARN(TAG, "Failed to get file table entry. %s", strerror(errno));
+        return -1;
+    }
+
+    // Get the file from the llfs filesystem associated with the stream
+    llfs_file = (llfs_file_t*)stream->_cookie;
+    if (llfs_file == NULL) {
+        LOG_WARN(TAG, "Failed to get llfs file associated with stream: %d", file_id);
+        return -1;
+    }
+
+    // Calculate the number of bytes to read (limited by the file size)
+    bytes_read = llfs_file->len - stream->_offset;
+    if (bytes_read > len) {
+        bytes_read = len;
+    } else if (bytes_read == 0) { // End of file
+        stream->_flags |= __SEOF;
+        return 0;
+    }
+
+    // Copy the data over to the dst buffer
+    memcpy(ptr, llfs_file->data + stream->_offset, bytes_read);
+
+    stream->_offset += (off_t)bytes_read;
+    return (int)bytes_read;
+}
+
+/**
+ * @brief Newlib isatty implementation
+ *
+ * @param file
+ * @return 1 if the file is stdin, stdout or stderr, 0 otherwise
+ */
+int isatty(int file) {
+    if (file == STDIN_FILENO || file == STDOUT_FILENO || file == STDERR_FILENO) {
+        return 1;
+    }
+
+    return 0;
+}
+
+/**
+ * @brief Newlib lseek implementation
+ *
+ * @param file
+ * @param ptr
+ * @param dir
+ * @return
+ */
+int _lseek(int file, int ptr, int dir) {
+    FILE* stream;
+
+    if (file == STDIN_FILENO || file == STDOUT_FILENO || file == STDERR_FILENO) {
+        LOG_DEBUG(TAG, "Trying to seek stdin, stdout or stderr: %d", file);
+        return -1;
+    }
+
+    stream = file_id_to_stream(file);
+    if (stream == NULL) {
+        LOG_WARN(TAG, "Failed to get file table entry. %s", strerror(errno));
+        return -1;
+    }
+
+    switch (dir) {
+        case SEEK_SET:
+            stream->_offset = ptr;
+            break;
+        case SEEK_CUR:
+            stream->_offset += ptr;
+            break;
+        case SEEK_END:
+            stream->_offset = (off_t)((llfs_file_t*)stream->_cookie)->len + ptr;
+            break;
+        default:
+            LOG_WARN(TAG, "Invalid seek direction: %d", dir);
+            return -1;
+    }
+
+    return 0;
+}
+
+/**
+ * @brief Newlib fstat implementation
+ *
+ * @param[in] file
+ * @param[out] st
+ * @return
+ */
+int _fstat(int file, struct stat* st) {
+    FILE* stream;
+    llfs_file_t *llfs_file;
+
+    // Check if the file is stdin, stdout or stderr
+    if (file == STDIN_FILENO || file == STDOUT_FILENO || file == STDERR_FILENO) {
+        st->st_mode = S_IFCHR; // Character special file
+        return 0;
+    }
+
+    // Get the stream associated with the file id
+    stream = file_id_to_stream(file);
+    if (stream == NULL) {
+        LOG_WARN(TAG, "Failed to get file table entry. %s", strerror(errno));
+        return -1;
+    }
+
+    // Get the file from the llfs filesystem associated with the stream
+    llfs_file = (llfs_file_t*)stream->_cookie;
+    if (llfs_file == NULL) {
+        LOG_WARN(TAG, "Failed to get llfs file associated with stream: %d", file);
+        return -1;
+    }
+
+    st->st_mode = S_IFREG;  // Regular file
+    st->st_size = (off_t)llfs_file->len;
+    return 0;
+}
+
+/**
+ * @brief Create a new entry in the file table
+ *
+ * @return The file id or -1 if an error occurred. See errno for more information.
+ */
+static int new_file_table_entry(void) {
+    FILE* stream;
+
+    // Try to find an empty entry in the file table
+    for (int i = 0; i < POSIX_MAX_FILES; i++) {
+        if (file_table[i] == NULL) {
+            stream = (FILE*)malloc(sizeof(FILE));
+            if (stream == NULL) {
+                errno = ENOMEM; // Out of memory
+                return -1;
+            }
+            file_table[i] = stream;
+            return i;
+        }
+    }
+
+    // No empty entry found
+    errno = ENFILE; // Too many open files
+    return -1;
+}
+
+/**
+ * @brief Remove an entry from the file table
+ *
+ * @param[in] file_id The file id to remove
+ * @return 0 if successful, -1 if an error occurred. See errno for more information.
+ */
+static int free_file_table_entry(int file_id) {
+    // Check if the file id is valid
+    if (file_id < 0 || file_id >= POSIX_MAX_FILES) {
+        errno = EBADF; // Bad file number
+        return -1;
+    }
+
+    // Remove the entry from the file table
+    free(file_table[file_id]);
+    file_table[file_id] = NULL;
+
+    return 0;
+}
+
+/**
+ * @brief Get the stream associated with a file id
+ *
+ * @param[in] file_id The file id to get the stream for
+ * @return The stream or NULL if an error occurred. See errno for more information.
+ */
+static FILE* file_id_to_stream(int file_id) {
+    if (file_id < 0 || file_id >= POSIX_MAX_FILES) {
+        errno = EBADF; // Bad file number
+        return NULL;
+    }
+    return file_table[file_id];
+}
+
+
+
+/**
+ * @brief Check if a filename ends with a given extension
+ *
+ * @param[in] filename The filename to check
+ * @param[in] ext The extension to check for
+ * @return 1 if the filename ends with the extension, 0 otherwise
+ */
+static uint8_t file_ext_cmp(const char* const filename, const char* const ext) {
+    uint8_t ext_len = strlen(ext);
+    uint8_t filename_len = strlen(filename);
+
+    if (filename_len < ext_len) {
+        return 0;
+    }
+
+    // Compare backwards
+    for (uint8_t i = 0; i < ext_len; i++) {
+        if (filename[filename_len - i] != ext[ext_len - i]) {
+            return 0;
+        }
+    }
+    return 1;
+}

project/Core/Src/main.c

@@ -24,8 +24,10 @@
 /* USER CODE BEGIN Includes */
 #define LOGGER_LEVEL_ALL
 #include "log.h"
-
+#include "llfs.h"
+#include "../../Drivers/BSP/STM32746G-Discovery/stm32746g_discovery_lcd.h"
 #include "lcd_api.h"
+
 /* USER CODE END Includes */
 
 /* Private typedef -----------------------------------------------------------*/
@@ -112,6 +114,153 @@ int main(void)
   MX_QUADSPI_Init();
   /* USER CODE BEGIN 2 */
   lcd_init(true);
+  
+  llfs_init();
+
+
+    FILE *f = fopen("test.txt", "rw");
+    if (f == NULL) {
+        LOG_INFO(TAG, "File not found test.txt");
+        return 1;
+    } else {
+        LOG_INFO(TAG, "File found test.txt");
+    }
+
+    // Test POSIX file operations
+    // fgetc
+    int c;
+    printf("Printing file:\n");
+    while ((c = fgetc(f)) != EOF) {
+        printf("%c", c);
+    }
+    LOG_INFO(TAG, "File printed");
+
+    // fseek
+    fseek(f, 0, SEEK_SET);
+    LOG_INFO(TAG, "File seeked to start");
+
+    // ftell
+    long pos = ftell(f);
+    LOG_INFO(TAG, "File position: %d", pos);
+
+    // fread
+    char buf[100];
+    size_t bytes_read = fread(buf, 1, 100, f);
+    LOG_INFO(TAG, "Read %d bytes from file", bytes_read);
+    printf("Read from file:\n");
+    for (int i = 0; i < bytes_read; i++) {
+        printf("%c", buf[i]);
+    }
+
+    // Rewind the file
+    LOG_INFO(TAG, "Before File rewinded, pos: %d", ftell(f));
+    rewind(f);
+    LOG_INFO(TAG, "File rewinded, pos: %d", ftell(f));
+
+    // Get the file size fstat
+    struct stat st;
+    fstat(fileno(f), &st);
+    LOG_INFO(TAG, "File size: %d", st.st_size);
+
+
+    // Get a list of all files with the .bmp extension
+    llfs_file_t file_list[10];
+    size_t num_files = llfs_file_list(file_list, 10, "*.bmp");
+    LOG_INFO(TAG, "Found %d files with the .bmp extension", num_files);
+    for (int i = 0; i < num_files; i++) {
+        LOG_INFO(TAG, "File %d: %s", i, file_list[i].name);
+    }
+
+    // Get a list of files with .txt or .html
+    num_files = llfs_file_list(file_list, 10, "*.txt");
+    LOG_INFO(TAG, "Found %d files with the .txt or .html extension", num_files);
+    for (int i = 0; i < num_files; i++) {
+        LOG_INFO(TAG, "File %d: %s", i, file_list[i].name);
+    }
+
+    // Loop over all files using the iterator
+    LOG_INFO(TAG, "Looping over all files, using the iterator");
+    void *mem = NULL;
+    llfs_file_t *file;
+    while ((file = llfs_next_file(&mem, NULL)) != NULL) {
+        LOG_INFO(TAG, "File: %s", file->name);
+    }
+
+    // Loop over all files with the .bmp extension using the iterator
+    LOG_INFO(TAG, "Looping over all files with the .bmp extension, using the iterator");
+    mem = NULL;
+    while ((file = llfs_next_file(&mem, "*.bmp")) != NULL) {
+        LOG_INFO(TAG, "File: %s", file->name);
+    }
+
+    // Get the number of files in the filesystem
+    size_t num_files_in_fs = llfs_file_count();
+    LOG_INFO(TAG, "Number of files in the filesystem: %d", num_files_in_fs);
+
+
+    fclose(f);
+
+    // Try opening multiple files
+    LOG_INFO(TAG, "Opening an closing multiple files");
+    FILE * f1 = fopen("test.txt", "rw");
+    if (f1 == NULL) {
+        LOG_INFO(TAG, "File not found f1");
+        return 1;
+    } else {
+        LOG_INFO(TAG, "File found f1");
+    }
+    // Get the fileno
+    int fd = fileno(f1);
+    LOG_INFO(TAG, "File descriptor f1: %d", fd);
+
+    FILE * f2 = fopen("test.txt", "rw");
+    if (f2 == NULL) {
+        LOG_INFO(TAG, "File not found f2");
+        return 1;
+    } else {
+        LOG_INFO(TAG, "File found f2");
+    }
+    // Get the fileno
+    fd = fileno(f2);
+    LOG_INFO(TAG, "File descriptorf2: %d", fd);
+
+    LOG_INFO(TAG, "Closing f1");
+    fclose(f1);
+
+    FILE * f3 = fopen("test.txt", "rw");
+    if (f3 == NULL) {
+        LOG_INFO(TAG, "File not found f3");
+        return 1;
+    } else {
+        LOG_INFO(TAG, "File found f3");
+    }
+    // Get the fileno
+    fd = fileno(f3);
+    LOG_INFO(TAG, "File descriptor f3: %d", fd);
+
+    LOG_INFO(TAG, "Closing f2");
+    fclose(f2);
+
+    LOG_INFO(TAG, "Closing f3");
+    fclose(f3);
+
+    // Try opening a file multiple times, until it fails
+    int i = 0;
+    LOG_INFO(TAG, "Opening a file multiple times, until it fails");
+    while (1) {
+        f = fopen("test.txt", "rw");
+        LOG_INFO(TAG, "File descriptor: %d", fileno(f));
+        if (f == NULL) {
+            LOG_INFO(TAG, "File not found test.txt");
+            break;
+        } else {
+            LOG_INFO(TAG, "File found test.txt");
+        }
+        i++;
+    }
+    LOG_INFO(TAG, "File opened %d times", i);
+
+
   /* USER CODE END 2 */
   /* Infinite loop */
   /* USER CODE BEGIN WHILE */

project/Core/Src/syscalls.c

@@ -89,14 +89,14 @@ __attribute__((weak)) int _write(int file, char *ptr, int len)
   return len;
 }
 
-int _close(int file)
+__attribute__((weak)) int _close(int file)
 {
   (void)file;
   return -1;
 }
 
 
-int _fstat(int file, struct stat *st)
+__attribute__((weak)) int _fstat(int file, struct stat *st)
 {
   (void)file;
   st->st_mode = S_IFCHR;
@@ -109,7 +109,7 @@ int _isatty(int file)
   return 1;
 }
 
-int _lseek(int file, int ptr, int dir)
+__attribute__((weak)) int _lseek(int file, int ptr, int dir)
 {
   (void)file;
   (void)ptr;
@@ -117,7 +117,7 @@ int _lseek(int file, int ptr, int dir)
   return 0;
 }
 
-int _open(char *path, int flags, ...)
+__attribute__((weak)) int _open(char *path, int flags, ...)
 {
   (void)path;
   (void)flags;
@@ -145,7 +145,7 @@ int _times(struct tms *buf)
   return -1;
 }
 
-int _stat(char *file, struct stat *st)
+__attribute__((weak)) int _stat(char *file, struct stat *st)
 {
   (void)file;
   st->st_mode = S_IFCHR;