feat(newlib): implement scandir and alphasort

Based on https://man7.org/linux/man-pages/man3/scandir.3.html

components/newlib/CMakeLists.txt

@@ -26,7 +26,9 @@ set(srcs
     "stdatomic.c"
     "time.c"
     "sysconf.c"
-    "realpath.c")
+    "realpath.c"
+    "scandir.c"
+)
 set(include_dirs platform_include)
 
 if(CONFIG_SPIRAM_CACHE_WORKAROUND)

components/newlib/platform_include/sys/dirent.h

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2015-2022 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2015-2024 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -55,6 +55,10 @@ void seekdir(DIR* pdir, long loc);
 void rewinddir(DIR* pdir);
 int closedir(DIR* pdir);
 int readdir_r(DIR* pdir, struct dirent* entry, struct dirent** out_dirent);
+int scandir(const char *dirname, struct dirent ***out_dirlist,
+    int (*select_func)(const struct dirent *),
+    int (*cmp_func)(const struct dirent **, const struct dirent **));
+int alphasort(const struct dirent **d1, const struct dirent **d2);
 
 #ifdef __cplusplus
 }

components/newlib/scandir.c

@@ -0,0 +1,78 @@
+/*
+ * SPDX-FileCopyrightText: 2023 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <stdlib.h>
+#include <string.h>
+#include <dirent.h>
+#include "esp_check.h"
+#include "esp_log.h"
+
+static const char *TAG = "scandir";
+
+int alphasort(const struct dirent **lhs, const struct dirent **rhs)
+{
+    return strcoll((*lhs)->d_name, (*rhs)->d_name);
+}
+
+int scandir(const char *dirname, struct dirent ***out_dirlist,
+            int (*select_func)(const struct dirent *),
+            int (*cmp_func)(const struct dirent **, const struct dirent **))
+{
+    DIR *dir_ptr = NULL;
+    struct dirent *entry;
+    size_t num_entries = 0;
+    size_t array_size = 8;  /* initial estimate */
+    struct dirent **entries = NULL;
+    int ret = -1;
+
+    entries = malloc(array_size * sizeof(struct dirent *));
+    ESP_RETURN_ON_FALSE(entries, -1, TAG, "Malloc failed for entries");
+
+    dir_ptr = opendir(dirname);
+    ESP_GOTO_ON_FALSE(dir_ptr, -1, out, TAG, "Failed to open directory: %s", dirname);
+
+    while ((entry = readdir(dir_ptr)) != NULL) {
+        /* skip entries that don't match the filter function */
+        if (select_func != NULL && !select_func(entry)) {
+            continue;
+        }
+
+        struct dirent *entry_copy = malloc(sizeof(struct dirent));
+        ESP_GOTO_ON_FALSE(entry_copy, -1, out, TAG, "Malloc failed for entry_copy");
+
+        *entry_copy = *entry;
+        entries[num_entries++] = entry_copy;
+
+        /* grow the array size if it's full */
+        if (num_entries >= array_size) {
+            array_size *= 2;
+            struct dirent **new_entries = realloc(entries, array_size * sizeof(struct dirent *));
+            ESP_GOTO_ON_FALSE(new_entries, -1, out, TAG, "Realloc failed for entries");
+            entries = new_entries;
+        }
+    }
+
+    /* sort the entries if a comparison function is provided */
+    if (num_entries && cmp_func) {
+        qsort(entries, num_entries, sizeof(struct dirent *),
+              (int (*)(const void *, const void *))cmp_func);
+    }
+
+    *out_dirlist = entries;
+    ret = num_entries;
+
+out:
+    if (ret < 0) {
+        while (num_entries > 0) {
+            free(entries[--num_entries]);
+        }
+        free(entries);
+    }
+    if (dir_ptr) {
+        closedir(dir_ptr);
+    }
+    return ret;
+}

components/newlib/test_apps/newlib/main/test_misc.c

@@ -12,8 +12,11 @@
 #include <errno.h>
 #include <sys/param.h>
 #include <stdlib.h>
+#include <dirent.h>
+#include "sys/dirent.h"
 #include "unity.h"
 #include "esp_heap_caps.h"
+#include "esp_vfs.h"
 
 
 TEST_CASE("misc - posix_memalign", "[newlib_misc]")
@@ -91,3 +94,90 @@ TEST_CASE("misc - realpath", "[newlib_misc]")
     TEST_ASSERT_EQUAL_STRING("/abc/def", out_new);
     free(out_new);
 }
+
+static int s_select_calls = 0;
+
+typedef struct {
+    const char **filenames;
+    size_t num_files;
+    size_t current_index;
+} scandir_test_dir_context_t;
+
+static DIR *scandir_test_opendir(void* ctx, const char* name)
+{
+    scandir_test_dir_context_t *dir_ctx = (scandir_test_dir_context_t *)ctx;
+    dir_ctx->current_index = 0;
+    static DIR dir = {};
+    return &dir;
+}
+
+static struct dirent *scandir_test_readdir(void* ctx, DIR* pdir)
+{
+    scandir_test_dir_context_t *dir_ctx = (scandir_test_dir_context_t *)ctx;
+    if (dir_ctx->current_index >= dir_ctx->num_files) {
+        return NULL;
+    }
+
+    static struct dirent entry;
+    snprintf(entry.d_name, sizeof(entry.d_name), "%s", dir_ctx->filenames[dir_ctx->current_index]);
+    dir_ctx->current_index++;
+    return &entry;
+}
+
+static int scandir_test_closedir(void* ctx, DIR* pdir)
+{
+    return 0;
+}
+
+static int scandir_test_select(const struct dirent *entry)
+{
+    s_select_calls++;
+    return strstr(entry->d_name, "test") != NULL;
+}
+
+TEST_CASE("file - scandir", "[newlib_misc]")
+{
+    const char *test_filenames[] = {
+        ".",
+        "..",
+        "test_file1.txt",
+        "file2.txt",
+        "test_file3.txt",
+        "test_file4.txt",
+        "test_file5.txt",
+        "test_file6.txt",
+        "test_file7.txt",
+        "test_file8.txt",
+        "test_file9.txt",
+        "test_file10.txt",
+    };
+    size_t num_test_files = sizeof(test_filenames) / sizeof(test_filenames[0]);
+
+    scandir_test_dir_context_t scandir_test_dir_ctx = { .filenames = test_filenames, .num_files = num_test_files };
+
+    const esp_vfs_t scandir_test_vfs = {
+        .flags = ESP_VFS_FLAG_CONTEXT_PTR,
+        .opendir_p = scandir_test_opendir,
+        .readdir_p = scandir_test_readdir,
+        .closedir_p = scandir_test_closedir
+    };
+
+    TEST_ESP_OK(esp_vfs_register("/data", &scandir_test_vfs, &scandir_test_dir_ctx));
+
+    struct dirent **namelist;
+    s_select_calls = 0;
+    int n = scandir("/data", &namelist, scandir_test_select, alphasort);
+    TEST_ASSERT_NOT_NULL(namelist);
+    TEST_ASSERT_GREATER_THAN(0, n);
+
+    TEST_ASSERT_EQUAL(num_test_files, s_select_calls);
+    TEST_ASSERT_EQUAL(9, n);
+
+    for (int i = 0; i < n; ++i) {
+        TEST_ASSERT_NOT_NULL(strstr(namelist[i]->d_name, "test"));
+        free(namelist[i]);
+    }
+    free(namelist);
+
+    esp_vfs_unregister("/data");
+}