win32: add local dirent implementation

Add a cut down version of the dirent implementation from git.
The git developers said:

  The mingw-runtime implemenation of opendir, readdir and closedir
  sets errno to 0 on success, something that POSIX explicitly
  forbids.

This also avoids having to link against libssp.a (commit 13eb34205)
and reduces the size of the binary by 2KB.

4 files changed, 117 insertions, 1 deletions

diff --git a/Makefile.flags b/Makefile.flags
index 0950ddb0d..2687781f1 100644
--- a/Makefile.flags
+++ b/Makefile.flags
@@ -149,7 +149,7 @@ endif
 ifeq ($(CONFIG_PLATFORM_MINGW32),y)
 CFLAGS += -Iwin32 -DHAVE_STRING_H=1 -DHAVE_CONFIG_H=0 -fno-builtin-stpcpy -fno-builtin-stpncpy -fno-ident -fno-builtin-strndup
 EXEEXT = .exe
-LDLIBS += ws2_32 mingwex -l:libssp.a
+LDLIBS += ws2_32
 endif
 
 ifneq ($(CONFIG_PLATFORM_MINGW32),y)
diff --git a/win32/Kbuild b/win32/Kbuild
index f3d0244d2..cabd70849 100644
--- a/win32/Kbuild
+++ b/win32/Kbuild
@@ -4,6 +4,7 @@
 
 lib-y:=
 
+lib-$(CONFIG_PLATFORM_MINGW32) += dirent.o
 lib-$(CONFIG_PLATFORM_MINGW32) += env.o
 lib-$(CONFIG_PLATFORM_MINGW32) += fnmatch.o
 lib-$(CONFIG_PLATFORM_MINGW32) += fsync.o
diff --git a/win32/dirent.c b/win32/dirent.c
new file mode 100644
index 000000000..b7de19391
--- /dev/null
+++ b/win32/dirent.c
@@ -0,0 +1,96 @@
+#include "libbb.h"
+
+struct DIR {
+        struct dirent dd_dir;
+        HANDLE dd_handle;     /* FindFirstFile handle */
+        int dd_stat;          /* 0-based index */
+};
+
+static inline void finddata2dirent(struct dirent *ent, WIN32_FIND_DATAA *fdata)
+{
+        /* copy file name from WIN32_FIND_DATA to dirent */
+        strcpy(ent->d_name, fdata->cFileName);
+}
+
+DIR *opendir(const char *name)
+{
+        char pattern[MAX_PATH];
+        WIN32_FIND_DATAA fdata;
+        HANDLE h;
+        int len;
+        DIR *dir;
+
+        /* check that name is not NULL */
+        if (!name) {
+                errno = EINVAL;
+                return NULL;
+        }
+        /* check that the pattern won't be too long for FindFirstFileA */
+        len = strlen(name);
+        if (len + 2 >= MAX_PATH) {
+                errno = ENAMETOOLONG;
+                return NULL;
+        }
+        /* copy name to temp buffer */
+        strcpy(pattern, name);
+
+        /* append optional '/' and wildcard '*' */
+        if (len && !is_dir_sep(pattern[len - 1]))
+                pattern[len++] = '/';
+        pattern[len++] = '*';
+        pattern[len] = 0;
+
+        /* open find handle */
+        h = FindFirstFileA(pattern, &fdata);
+        if (h == INVALID_HANDLE_VALUE) {
+                DWORD err = GetLastError();
+                errno = (err == ERROR_DIRECTORY) ? ENOTDIR : err_win_to_posix();
+                return NULL;
+        }
+
+        /* initialize DIR structure and copy first dir entry */
+        dir = xmalloc(sizeof(DIR));
+        dir->dd_handle = h;
+        dir->dd_stat = 0;
+        finddata2dirent(&dir->dd_dir, &fdata);
+        return dir;
+}
+
+struct dirent *readdir(DIR *dir)
+{
+        if (!dir) {
+                errno = EBADF; /* No set_errno for mingw */
+                return NULL;
+        }
+
+        /* if first entry, dirent has already been set up by opendir */
+        if (dir->dd_stat) {
+                /* get next entry and convert from WIN32_FIND_DATA to dirent */
+                WIN32_FIND_DATAA fdata;
+                if (FindNextFileA(dir->dd_handle, &fdata)) {
+                        finddata2dirent(&dir->dd_dir, &fdata);
+                } else {
+                        DWORD lasterr = GetLastError();
+                        /* POSIX says you shouldn't set errno when readdir can't
+                           find any more files; so, if another error we leave it set. */
+                        if (lasterr != ERROR_NO_MORE_FILES)
+                                errno = err_win_to_posix();
+                        return NULL;
+                }
+        }
+
+        ++dir->dd_stat;
+        return &dir->dd_dir;
+}
+
+int closedir(DIR *dir)
+{
+        if (!dir) {
+                errno = EBADF;
+                return -1;
+        }
+
+        FindClose(dir->dd_handle);
+        free(dir);
+        return 0;
+}
diff --git a/win32/dirent.h b/win32/dirent.h
new file mode 100644
index 000000000..b38d0d133
--- /dev/null
+++ b/win32/dirent.h
@@ -0,0 +1,19 @@
+#ifndef DIRENT_H
+#define DIRENT_H
+
+typedef struct DIR DIR;
+
+#define DT_UNKNOWN 0
+#define DT_DIR     1
+#define DT_REG     2
+#define DT_LNK     3
+
+struct dirent {
+        char d_name[PATH_MAX];  // file name
+};
+
+DIR *opendir(const char *dirname);
+struct dirent *readdir(DIR *dir);
+int closedir(DIR *dir);
+
+#endif /* DIRENT_H */