CST-agent/include/os_compat.h

#ifndef CST_OS_COMPAT_H
#define CST_OS_COMPAT_H

#include <stddef.h>
#include <time.h>

#ifdef __cplusplus
extern "C" {
#endif

#ifndef OS_PATH_MAX
#define OS_PATH_MAX 4096
#endif

/* --- path --- */
int os_path_is_abs(const char *p);
/* Join with native separator; out always uses '/' on Unix and '\\' on Win for
 * the joiner, but os_path_norm_slashes converts to '/' for comparisons. */
int os_path_join(char *out, size_t out_sz, const char *a, const char *b);
void os_path_norm_slashes(char *p);
int os_realpath(const char *path, char *out, size_t out_sz);
/* True if path is under root (after realpath/norm). Trailing slash rules apply. */
int os_path_under(const char *root, const char *path);

/* --- dirs / config --- */
int os_mkdir(const char *path, int mode);
int os_mkdir_p(const char *path, int mode);
int os_config_dir(char *out, size_t out_sz);
int os_temp_dir(char *out, size_t out_sz);
/* Create unique temp file; writes path into out; returns fd or -1. Caller closes. */
int os_mkstemp(char *out, size_t out_sz, const char *prefix);

/* Directory containing the running executable (for bundled busybox).
 * Call os_set_prog_path(argv[0]) early on Unix/Termux as fallback. */
void os_set_prog_path(const char *argv0);
int os_exe_dir(char *out, size_t out_sz);

/* Resolve shell interpreter path into out.
 * Order: CST_SHELL → <exe_dir>/busybox[.exe] → /bin/sh (Unix). */
int os_resolve_shell(char *out, size_t out_sz);

/* --- process --- */
typedef struct {
  char *out;
  size_t out_len;
  int exit_code;
} os_run_result_t;

void os_run_result_free(os_run_result_t *r);

/* Run argv[0..] (NULL-terminated) with cwd; capture stdout+stderr.
 * max_out caps captured bytes (0 = default 512KiB). */
int os_run_capture(const char *cwd, const char *const argv[], size_t max_out,
                   os_run_result_t *r);

/* Convenience: shell -c cmd via os_resolve_shell. */
int os_run_shell_c(const char *cwd, const char *cmd, size_t max_out,
                   os_run_result_t *r);

/* Same, with child_hook(ud) run in the child just before exec (Unix only;
 * ignored on Windows). A non-zero return aborts the child with exit 126. */
typedef int (*os_child_hook_fn)(void *ud);
int os_run_capture_ex(const char *cwd, const char *const argv[],
                      size_t max_out, os_run_result_t *r,
                      os_child_hook_fn child_hook, void *ud);
int os_run_shell_ex(const char *cwd, const char *cmd, size_t max_out,
                    os_run_result_t *r, os_child_hook_fn child_hook,
                    void *ud);

/* Child processes get stdin=/dev/null, their own process group, and are
 * killed after the timeout (CST_SHELL_TIMEOUT seconds, default 120) or when
 * *flag becomes non-zero. Exit code 124 = timeout, 130 = cancelled. */
void os_set_cancel_flag(volatile int *flag);
volatile int *os_get_cancel_flag(void);
void os_set_run_timeout(int seconds); /* this thread; 0 = default */
int os_get_run_timeout(void);

/* Long-lived child with pipes on stdin/stdout (MCP servers). stderr goes
 * to stderr_path (NULL = discarded). env_add: "KEY=VALUE" entries added to
 * the inherited environment (NULL-terminated, may be NULL). */
typedef struct {
#ifdef _WIN32
  void *proc, *in_w, *out_r;
#else
  int pid, in_fd, out_fd;
#endif
} os_proc_t;
int os_proc_spawn(const char *cwd, const char *const argv[],
                  const char *const env_add[], const char *stderr_path,
                  os_proc_t *p);
int os_proc_write(os_proc_t *p, const char *data, size_t n); /* 0 / -1 */
/* Bytes read, 0 at EOF, -1 on error, -2 when nothing came within
 * timeout_ms. */
long os_proc_read(os_proc_t *p, char *buf, size_t n, int timeout_ms);
void os_proc_close_stdin(os_proc_t *p);
/* Close the pipes, end the process (group) and reap it. */
void os_proc_kill(os_proc_t *p);
/* This thread's cancel flag (os_set_cancel_flag) is raised. */
int os_cancel_requested(void);

/* Run fn(args[i]) for every i on its own thread and wait for all of them
 * (falls back to running inline when a thread cannot start). */
typedef void (*os_task_fn)(void *arg);
void os_run_parallel(os_task_fn fn, void *const args[], int n);

/* Monotonic milliseconds (arbitrary epoch). */
double os_now_ms(void);

/* --- misc --- */
void os_localtime(const time_t *t, struct tm *out);
int os_getpid(void);
int os_chmod_private(const char *path); /* best-effort 0600; no-op/ok on Win */

/* --- UTF-8 --------------------------------------------------------------
 * Encode one code point as UTF-8, independent of the C locale.
 *
 * wcrtomb() follows setlocale(). On Linux the environment normally selects a
 * UTF-8 locale, but on Windows the C runtime maps setlocale(LC_ALL, "") to the
 * ANSI code page -- 936 (GBK) on a Chinese system -- so wcrtomb() hands back
 * GBK bytes where the protocol requires UTF-8, and the model receives
 * mojibake. Windows' C runtime has no ".UTF-8" locale to switch to.
 *
 * Returns the number of bytes written (1..4), or 0 if the code point cannot be
 * encoded. Surrogate halves (as they arrive on 16-bit wchar_t platforms for
 * non-BMP code points) return 0 and are skipped. */
int os_utf8_encode(unsigned long cp, char out[4]);

/* Decode one UTF-8 sequence from s (at most avail bytes).
 * Returns the number of bytes consumed (1..4) and stores the code point in
 * *cp, or 0 if the bytes are not a valid, complete, non-overlong sequence.
 *
 * The counterpart of the encoder above, and needed for the same reason:
 * mbrtowc() also follows setlocale(), so on Windows it would decode UTF-8
 * text as GBK and the screen would show mojibake. */
int os_utf8_decode(const char *s, size_t avail, unsigned long *cp);

/* --- libc gaps on Windows ------------------------------------------------
 * MinGW-w64 provides neither strcasestr() (a GNU extension) nor
 * setenv()/unsetenv() (POSIX): they are simply absent from its headers.
 * src/tui.c uses all three. Implemented in os_compat.c for _WIN32 only,
 * so the Unix builds keep using the libc versions. */
#if defined(_WIN32)
char *strcasestr(const char *haystack, const char *needle);
int setenv(const char *name, const char *value, int overwrite);
int unsetenv(const char *name);
#endif

#ifdef __cplusplus
}
#endif

#endif /* CST_OS_COMPAT_H */