From 7b5edf6e8d4133db6b98f1c8cdea95ac4380f810 Mon Sep 17 00:00:00 2001
From: Max Wash <mbswash@gmail.com>
Date: Tue, 17 May 2022 20:58:47 +0100
Subject: [PATCH] Implemented buffering int readdir()

---
 photon/libc/sys/horizon/dirent.c      | 126 +++++++++++++++++++-------
 photon/libc/sys/horizon/sys/_dirent.h |  13 ++-
 2 files changed, 106 insertions(+), 33 deletions(-)

diff --git a/photon/libc/sys/horizon/dirent.c b/photon/libc/sys/horizon/dirent.c
index f55614b..15d0c4c 100644
--- a/photon/libc/sys/horizon/dirent.c
+++ b/photon/libc/sys/horizon/dirent.c
@@ -30,66 +30,128 @@ DIR *opendir(const char *path)
 int closedir(DIR *d)
 {
     close(d->fd);
+    for (int i = 0; i < d->cache_size; i++) {
+        if (d->dent_cache[i].d_namep) {
+            free(d->dent_cache[i].d_namep);
+        }
+    }
+
     free(d);
     return 0;
 }
 
-struct dirent *readdir(DIR *d)
+static void clear_cache(DIR *d)
 {
-    mio_dirent dent;
-    int r = mio_getdents(d->fd, &dent, 1);
-    if (r < 1) {
-        __set_errno(-r);
-        return NULL;
+    for (int i = 0; i < d->cache_size; i++) {
+        if (d->dent_cache[i].d_namep) {
+            free(d->dent_cache[i].d_namep);
+        }
+
+        d->dent_cache[i].d_namep = NULL;
     }
 
-    size_t name_max = sizeof(d->current_dent.d_name);
-    if (sizeof(dent.d_name) < name_max) {
-        name_max = sizeof(dent.d_name);
-    }
-
-    d->current_dent.d_ino = dent.d_ino;
-    d->current_dent.d_type = dent.d_type;
-    memcpy(d->current_dent.d_name, dent.d_name, name_max);
-
-    return &d->current_dent;
+    d->cache_size = d->cache_idx = 0;
 }
 
-int readdir_r(DIR *d, struct dirent *entry, struct dirent **result)
+static int refill(DIR *d)
 {
-    mio_dirent dent;
-    int r = mio_getdents(d->fd, &dent, 1);
-    if (r < 1) {
-        *result = NULL;
+    clear_cache(d);
+
+    for (int i = 0; i < d->cache_size; i++) {
+        free(d->dent_cache[i].d_namep);
+        d->dent_cache[i].d_namep = NULL;
+    }
+
+    d->cache_size = d->cache_idx = 0;
+    mio_dirent dent[__SYS_DENT_CACHE_SZ];
+
+    int r = mio_getdents(d->fd, dent, __SYS_DENT_CACHE_SZ);
+    if (r < 0) {
         __set_errno(-r);
         return -1;
     }
 
-    size_t name_max = sizeof(d->current_dent.d_name);
-    if (sizeof(dent.d_name) < name_max) {
-        name_max = sizeof(dent.d_name);
+    for (int i = 0; i < r; i++) {
+        struct __dentcache *cache_ent = &d->dent_cache[i];
+        cache_ent->d_ino = dent[i].d_ino;
+        cache_ent->d_type = dent[i].d_type;
+        cache_ent->d_namep = strdup(dent[i].d_name);
     }
 
-    d->current_dent.d_ino = dent.d_ino;
-    d->current_dent.d_type = dent.d_type;
-    memcpy(d->current_dent.d_name, dent.d_name, name_max);
-    memcpy(entry, &d->current_dent, sizeof(*entry));
-    *result = entry;
+    d->cache_idx = 0;
+    d->cache_size = r;
+    return 0;
+}
+
+static void fill_dirent(DIR *d, struct dirent *out)
+{
+    if (d->cache_idx >= d->cache_size) {
+        return;
+    }
+
+    struct __dentcache *cache_ent = &d->dent_cache[d->cache_idx];
+    out->d_ino = cache_ent->d_ino;
+    out->d_type = cache_ent->d_type;
+
+    if (cache_ent->d_namep) {
+        strncpy(out->d_name, cache_ent->d_namep, sizeof out->d_name - 1);
+        out->d_name[sizeof out->d_name - 1] = '\0';
+    }
+}
+
+struct dirent *readdir(DIR *d)
+{
+    if (d->cache_idx == d->cache_size) {
+        if (refill(d) != 0 || !d->cache_size) {
+            return NULL;
+        }
+    }
+
+    fill_dirent(d, &d->cdent);
+    d->cache_idx++;
+    d->seek++;
+    return &d->cdent;
+}
+
+int readdir_r(DIR *d, struct dirent *entry, struct dirent **result)
+{
+    if (d->cache_idx == d->cache_size) {
+        if (refill(d) != 0) {
+            return 1;
+        }
+
+        if (d->cache_size == 0) {
+            if (result) {
+                *result = NULL;
+            }
+
+            return 0;
+        }
+    }
+
+    fill_dirent(d, entry);
+    d->seek++;
+
+    if (result) {
+        *result = entry;
+    }
 
     return 0;
 }
 
 void rewinddir(DIR *d)
 {
-    mio_seek(d->fd, 0, SEEK_SET);
+    d->seek = mio_seek(d->fd, 0, SEEK_SET);
+    clear_cache(d);
 }
 
 void seekdir(DIR *d, long int off)
 {
-    mio_seek(d->fd, off, SEEK_SET);
+    d->seek = mio_seek(d->fd, off, SEEK_SET);
+    clear_cache(d);
 }
 
 long int telldir(DIR *d)
 {
-    return mio_seek(d->fd, 0, SEEK_CUR);
+    return d->seek;
 }
diff --git a/photon/libc/sys/horizon/sys/_dirent.h b/photon/libc/sys/horizon/sys/_dirent.h
index 6925c4e..e28841d 100644
--- a/photon/libc/sys/horizon/sys/_dirent.h
+++ b/photon/libc/sys/horizon/sys/_dirent.h
@@ -4,6 +4,14 @@
 #include <sys/types.h>
 #include <limits.h>
 
+#define __SYS_DENT_CACHE_SZ 4
+
+struct __dentcache {
+    ino_t d_ino;
+    unsigned char d_type;
+    char *d_namep;
+};
+
 struct dirent {
     ino_t d_ino;
     unsigned char d_type;
@@ -12,7 +20,10 @@ struct dirent {
 
 typedef struct {
     int fd;
-    struct dirent current_dent;
+    long seek;
+    unsigned char cache_idx, cache_size;
+    struct __dentcache dent_cache[__SYS_DENT_CACHE_SZ];
+    struct dirent cdent;
 } DIR;
 
 #endif