LibC: Implement getpw{nam,uid}_r

userspace/libraries/LibC/pwd.cpp

@@ -1,118 +1,142 @@
-#include <BAN/Assert.h>
-
 #include <ctype.h>
 #include <errno.h>
 #include <pwd.h>
-#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 
 static FILE* s_pwent_fp = nullptr;
 static passwd s_pwent_struct;
 
-static bool open_pwent()
-{
-	if (s_pwent_fp)
-		return true;
-	s_pwent_fp = fopen("/etc/passwd", "r");
-	return s_pwent_fp;
-}
-
-static void clear_pwent(passwd& passwd)
-{
-	if (passwd.pw_name)
-		free(passwd.pw_name);
-	passwd.pw_name = nullptr;
-	if (passwd.pw_dir)
-		free(passwd.pw_dir);
-	passwd.pw_dir = nullptr;
-	if (passwd.pw_shell)
-		free(passwd.pw_shell);
-	passwd.pw_shell = nullptr;
-}
+static char* s_pwent_buffer = nullptr;
+static size_t s_pwent_buffer_size = 0;
 
 void endpwent(void)
 {
-	if (!s_pwent_fp)
-		return;
+	if (s_pwent_fp)
 		fclose(s_pwent_fp);
 	s_pwent_fp = nullptr;
-	clear_pwent(s_pwent_struct);
+
+	if (s_pwent_buffer)
+		free(s_pwent_buffer);
+	s_pwent_buffer = nullptr;
+}
+
+void setpwent(void)
+{
+	if (!s_pwent_fp)
+		return;
+	fseek(s_pwent_fp, 0, SEEK_SET);
+}
+
+static int getpwent_impl(FILE* fp, struct passwd* pwd, char* buffer, size_t bufsize, struct passwd** result)
+{
+	for (;;)
+	{
+		if (fgets(buffer, bufsize, fp) == nullptr)
+		{
+			if (ferror(fp))
+				return errno;
+			*result = nullptr;
+			return 0;
+		}
+
+		const size_t line_len = strlen(buffer);
+		if (line_len == 0)
+			continue;
+
+		if (buffer[line_len - 1] == '\n')
+			buffer[line_len - 1] = '\0';
+		else if (!feof(fp))
+			return (errno = ERANGE);
+
+#define GET_STRING() ({ \
+			ptr = strchr(ptr, ':'); \
+			if (ptr == nullptr) \
+				continue; \
+			*ptr++ = '\0'; \
+		})
+
+#define GET_INT() ({ \
+				if (!isdigit(*ptr)) \
+					continue; \
+				long val = 0; \
+				while (isdigit(*ptr)) \
+					val = (val * 10) + (*ptr++ - '0'); \
+				if (*ptr != ':') \
+					continue; \
+				*ptr++ = '\0'; \
+				val; \
+			})
+
+		char* ptr = buffer;
+
+		pwd->pw_name = ptr;
+		GET_STRING();
+
+		pwd->pw_passwd = ptr;
+		GET_STRING();
+
+		pwd->pw_uid = GET_INT();
+
+		pwd->pw_gid = GET_INT();
+
+		pwd->pw_gecos = ptr;
+		GET_STRING();
+
+		pwd->pw_dir = ptr;
+		GET_STRING();
+
+		pwd->pw_shell = ptr;
+
+		*result = pwd;
+		return 0;
+	}
 }
 
 struct passwd* getpwent(void)
 {
-	if (!s_pwent_fp)
-		if (!open_pwent())
-			return nullptr;
-	clear_pwent(s_pwent_struct);
-
-	static char buffer[4096];
-	if (!fgets(buffer, sizeof(buffer), s_pwent_fp))
-		return nullptr;
-
-	size_t buffer_len = strlen(buffer);
-
-	ASSERT(buffer[buffer_len - 1] == '\n');
-	buffer[buffer_len - 1] = '\0';
-	buffer_len--;
-
-	const char* ptr = buffer;
-	for (int i = 0; i < 7; i++)
+	if (s_pwent_fp == nullptr)
 	{
-		char* end = strchr(ptr, ':');
-		ASSERT((i < 6) ? end != nullptr : end == nullptr);
-		if (!end)
-			end = buffer + buffer_len;
-		*end = '\0';
-
-		const size_t field_len = end - ptr;
-
-		switch (i)
-		{
-			case 0:
-				s_pwent_struct.pw_name = strndup(ptr, field_len + 1);
-				if (!s_pwent_struct.pw_name)
+		s_pwent_fp = fopen("/etc/passwd", "r");
+		if (s_pwent_fp == nullptr)
 			return nullptr;
-				break;
-			case 1:
-				s_pwent_struct.pw_passwd = strndup(ptr, field_len + 1);
-				if (!s_pwent_struct.pw_passwd)
-					return nullptr;
-				break;
-			case 2:
-				ASSERT(1 <= field_len && field_len <= 9);
-				for (size_t j = 0; j < field_len; j++)
-					ASSERT(isdigit(ptr[j]));
-				s_pwent_struct.pw_uid = atoi(ptr);
-				break;
-			case 3:
-				ASSERT(1 <= field_len && field_len <= 9);
-				for (size_t j = 0; j < field_len; j++)
-					ASSERT(isdigit(ptr[j]));
-				s_pwent_struct.pw_gid = atoi(ptr);
-				break;
-			case 4:
-				s_pwent_struct.pw_gecos = strndup(ptr, field_len + 1);
-				if (!s_pwent_struct.pw_gecos)
-					return nullptr;
-				break;
-			case 5:
-				s_pwent_struct.pw_dir = strndup(ptr, field_len + 1);
-				if (!s_pwent_struct.pw_dir)
-					return nullptr;
-				break;
-			case 6:
-				s_pwent_struct.pw_shell = strndup(ptr, field_len + 1);
-				if (!s_pwent_struct.pw_shell)
-					return nullptr;
-				break;
 	}
 
-		ptr = end + 1;
+	if (s_pwent_buffer == nullptr)
+	{
+		long size = sysconf(_SC_GETPW_R_SIZE_MAX);
+		if (size == -1)
+			size = 512;
+
+		s_pwent_buffer = static_cast<char*>(malloc(size));
+		if (s_pwent_buffer == nullptr)
+			return nullptr;
+		s_pwent_buffer_size = size;
 	}
 
-	return &s_pwent_struct;
+	const off_t old_offset = ftello(s_pwent_fp);
+
+	passwd* result;
+	for (;;)
+	{
+		const int error = getpwent_impl(s_pwent_fp, &s_pwent_struct, s_pwent_buffer, s_pwent_buffer_size, &result);
+		if (error == 0)
+			break;
+		fseeko(s_pwent_fp, old_offset, SEEK_SET);
+		if (error != ERANGE)
+			return nullptr;
+
+		const size_t new_size = s_pwent_buffer_size * 2;
+		char* new_buffer = static_cast<char*>(realloc(s_pwent_buffer, new_size));
+		if (new_buffer == nullptr)
+			return nullptr;
+
+		s_pwent_buffer = new_buffer;
+		s_pwent_buffer_size = new_size;
+	}
+
+	return result;
 }
 
 struct passwd* getpwnam(const char* name)
@@ -135,9 +159,44 @@ struct passwd* getpwuid(uid_t uid)
 	return nullptr;
 }
 
-void setpwent(void)
+int getpwuid_r(uid_t uid, struct passwd* pwd, char* buffer, size_t bufsize, struct passwd** result)
 {
-	if (!s_pwent_fp)
-		return;
-	fseek(s_pwent_fp, 0, SEEK_SET);
+	FILE* fp = fopen("/etc/passwd", "r");
+	if (fp == nullptr)
+		return errno;
+
+	int ret = 0;
+	for (;;)
+	{
+		if ((ret = getpwent_impl(fp, pwd, buffer, bufsize, result)))
+			break;
+		if (*result == nullptr)
+			break;
+		if (pwd->pw_uid == uid)
+			break;
+	}
+
+	fclose(fp);
+	return ret;
+}
+
+int getpwnam_r(const char* name, struct passwd* pwd, char* buffer, size_t bufsize, struct passwd** result)
+{
+	FILE* fp = fopen("/etc/passwd", "r");
+	if (fp == nullptr)
+		return errno;
+
+	int ret = 0;
+	for (;;)
+	{
+		if ((ret = getpwent_impl(fp, pwd, buffer, bufsize, result)))
+			break;
+		if (*result == nullptr)
+			break;
+		if (strcmp(pwd->pw_name, name) == 0)
+			break;
+	}
+
+	fclose(fp);
+	return ret;
 }