libc: minimal: stdin: Add getc() implementation and unit tests

include/zephyr/sys/libc-hooks.h

@@ -35,6 +35,8 @@ __syscall int zephyr_write_stdout(const void *buf, int nbytes);
 
 __syscall int zephyr_fputc(int c, FILE * stream);
 
+__syscall int zephyr_fgetc(FILE *stream);
+
 #ifdef CONFIG_MINIMAL_LIBC
 /* Minimal libc only */
 

lib/libc/minimal/CMakeLists.txt

@@ -28,6 +28,7 @@ zephyr_library_sources(
   source/string/strstr.c
   source/string/string.c
   source/string/strspn.c
+  source/stdin/stdin_console.c
   source/stdout/stdout_console.c
   source/stdout/sprintf.c
   source/stdout/fprintf.c

lib/libc/minimal/include/stdio.h

@@ -64,6 +64,9 @@ int remove(const char *path);
 #define putc(c, stream) fputc(c, stream)
 #define putchar(c) putc(c, stdout)
 
+int fgetc(FILE *stream);
+#define getc(stream) fgetc(stream)
+
 #ifdef __cplusplus
 }
 #endif

lib/libc/minimal/source/stdin/stdin_console.c

@@ -0,0 +1,151 @@
+/* stdin_console.c */
+
+/*
+ * Copyright (c) 2025 The Zephyr Project Contributors
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <stdio.h>
+#include <zephyr/sys/libc-hooks.h>
+#include <zephyr/internal/syscall_handler.h>
+#include <string.h>
+
+static unsigned char _stdin_hook_default(void)
+{
+	return 0;
+}
+
+static unsigned char (*_stdin_hook)(void) = _stdin_hook_default;
+
+void __stdin_hook_install(unsigned char (*hook)(void))
+{
+	_stdin_hook = hook;
+}
+
+int z_impl_zephyr_fgetc(FILE *stream)
+{
+	if (stream == stdin && _stdin_hook) {
+		return _stdin_hook();
+	}
+	return EOF;
+}
+
+#ifdef CONFIG_USERSPACE
+static inline int z_vrfy_zephyr_fgetc(FILE *stream)
+{
+	return z_impl_zephyr_fgetc(stream);
+}
+#include <zephyr/syscalls/zephyr_fgetc_mrsh.c>
+#endif
+
+int fgetc(FILE *stream)
+{
+	return zephyr_fgetc(stream);
+}
+
+char *fgets(char *s, int size, FILE *stream)
+{
+	if (s == NULL || size <= 0) {
+		return NULL;
+	}
+
+	int i = 0;
+	int c;
+
+	while (i < size - 1) {
+		c = fgetc(stream);
+		if (c == EOF) {
+			if (i == 0) {
+				return NULL;
+			}
+			break;
+		}
+		s[i++] = (char)c;
+		if (c == '\n') {
+			break;
+		}
+	}
+	s[i] = '\0';
+	return s;
+}
+
+#undef getc
+int getc(FILE *stream)
+{
+	return zephyr_fgetc(stream);
+}
+
+#undef getchar
+int getchar(void)
+{
+	return zephyr_fgetc(stdin);
+}
+
+size_t z_impl_zephyr_fread(void *ZRESTRICT ptr, size_t size, size_t nitems, FILE *ZRESTRICT stream)
+{
+	size_t i, j;
+	unsigned char *p = ptr;
+
+	if ((stream != stdin) || (nitems == 0) || (size == 0)) {
+		return 0;
+	}
+
+	i = nitems;
+	do {
+		j = size;
+		do {
+			int c = fgetc(stream);
+			if (c == EOF) {
+				goto done;
+			}
+			*p++ = (unsigned char)c;
+			j--;
+		} while (j > 0);
+
+		i--;
+	} while (i > 0);
+
+done:
+	return (nitems - i);
+}
+
+#ifdef CONFIG_USERSPACE
+static inline size_t z_vrfy_zephyr_fread(void *ZRESTRICT ptr, size_t size, size_t nitems,
+					 FILE *ZRESTRICT stream)
+{
+	K_OOPS(K_SYSCALL_MEMORY_ARRAY_WRITE(ptr, nitems, size));
+	return z_impl_zephyr_fread(ptr, size, nitems, stream);
+}
+#include <zephyr/syscalls/zephyr_fread_mrsh.c>
+#endif
+
+size_t fread(void *ZRESTRICT ptr, size_t size, size_t nitems, FILE *ZRESTRICT stream)
+{
+	return zephyr_fread(ptr, size, nitems, stream);
+}
+
+char *gets(char *s)
+{
+	if (s == NULL) {
+		return NULL;
+	}
+
+	int c;
+	char *p = s;
+
+	while (1) {
+		c = getchar();
+		if (c == EOF || c == '\n') {
+			break;
+		}
+		*p++ = (char)c;
+	}
+	*p = '\0';
+
+	// If nothing was read and EOF, return NULL
+	if (p == s && c == EOF) {
+		return NULL;
+	}
+	return s;
+}

tests/lib/sscanf/CMakeLists.txt

@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(sscanf)
+
+FILE(GLOB app_sources src/*.c)
+target_sources(app PRIVATE ${app_sources})

tests/lib/sscanf/prj.conf

@@ -0,0 +1,6 @@
+CONFIG_ZTEST=y
+CONFIG_FPU=y
+CONFIG_TEST_USERSPACE=y
+CONFIG_ZTEST_FATAL_HOOK=y
+CONFIG_PICOLIBC_IO_FLOAT=y
+CONFIG_ZTEST_STACK_SIZE=2048

tests/lib/sscanf/src/main.c

@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2025 The Zephyr Project Contributors
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * DESCRIPTION
+ * This module contains the code for testing input functionality in minimal libc,
+ * including getc(), fgetc(), fgets(), and getchar().
+ */
+
+#include <zephyr/ztest.h>
+#include <stdio.h>
+#include <string.h>
+
+static const char *test_input = "Hello\nWorld";
+static int input_pos;
+
+static int mock_stdin_hook(void)
+{
+	if (test_input[input_pos] == '\0') {
+		return EOF;
+	}
+	return test_input[input_pos++];
+}
+
+void setup_stdin_hook(void)
+{
+	input_pos = 0;
+	extern void __stdin_hook_install(int (*hook)(void));
+	__stdin_hook_install(mock_stdin_hook);
+}
+
+ZTEST(sscanf, test_getc)
+{
+	setup_stdin_hook();
+	int c = getc(stdin);
+	zassert_equal(c, 'H', "getc(stdin) did not return 'H'");
+	c = getc(stdin);
+	zassert_equal(c, 'e', "getc(stdin) did not return 'e'");
+}
+
+ZTEST(sscanf, test_fgetc)
+{
+	setup_stdin_hook();
+	int c = fgetc(stdin);
+	zassert_equal(c, 'H', "fgetc(stdin) did not return 'H'");
+	c = fgetc(stdin);
+	zassert_equal(c, 'e', "fgetc(stdin) did not return 'e'");
+}
+
+ZTEST(sscanf, test_getchar)
+{
+	setup_stdin_hook();
+	int c = getchar();
+	zassert_equal(c, 'H', "getchar() did not return 'H'");
+	c = getchar();
+	zassert_equal(c, 'e', "getchar() did not return 'e'");
+}
+
+ZTEST(sscanf, test_fgets)
+{
+	setup_stdin_hook();
+	char buf[16];
+	char *ret = fgets(buf, sizeof(buf), stdin);
+	zassert_not_null(ret, "fgets returned NULL");
+	zassert_true(strcmp(buf, "Hello\n") == 0, "fgets did not read 'Hello\\n'");
+	ret = fgets(buf, sizeof(buf), stdin);
+	zassert_not_null(ret, "fgets returned NULL on second call");
+	zassert_true(strcmp(buf, "World") == 0, "fgets did not read 'World'");
+}
+
+ZTEST_SUITE(sscanf, NULL, NULL, NULL, NULL, NULL);