libc: Add a basic implementation of pathconf()

libs/libc/include/unistd.h

@@ -6,15 +6,20 @@
 #include <luna/os-limits.h>
 #include <sys/types.h>
 
+// Standard IO streams.
 #define STDIN_FILENO 0  // The standard input stream.
 #define STDOUT_FILENO 1 // The standard output stream.
 #define STDERR_FILENO 2 // The standard error stream.
 
+// Possible arguments to access()
 #define F_OK 0 // Check for a file's existence.
 #define R_OK 1 // Check whether a file is readable.
 #define W_OK 2 // Check whether a file is writable.
 #define X_OK 4 // Check whether a file is executable.
 
+// Name values for pathconf()
+#define _PC_PATH_MAX 0 // Maximum length of a path relative to the provided name.
+
 #ifdef __cplusplus
 extern "C"
 {
@@ -103,6 +108,9 @@ extern "C"
     int chdir(const char* path);  // Not implemented.
     int pipe(int fd[2]);          // Not implemented.
 
+    /* Returns a configuration value for the file at path. */
+    long pathconf(const char* path, int name);
+
     /* Returns the maximum number of file descriptors a process can have open at the same time. */
     int getdtablesize(void);
 

libs/libc/src/unistd.cpp

@@ -164,6 +164,15 @@ extern "C"
         NOT_IMPLEMENTED("pipe");
     }
 
+    long pathconf(const char* path, int name)
+    {
+        switch (name)
+        {
+        case _PC_PATH_MAX: return PATH_MAX - (strlen(path) + 1);
+        default: errno = EINVAL; return -1;
+        }
+    }
+
     int getdtablesize(void)
     {
         return OPEN_MAX;