Implement MORE.COM command

src/dos/dos_programs.cpp

@@ -32,6 +32,7 @@
 #include "program_loadrom.h"
 #include "program_ls.h"
 #include "program_mem.h"
+#include "program_more.h"
 #include "program_mount.h"
 #include "program_placeholder.h"
 #include "program_rescan.h"
@@ -74,6 +75,7 @@ void Add_VFiles(const bool add_autoexec)
 	PROGRAMS_MakeFile("LOADROM.COM", ProgramCreate<LOADROM>);
 	PROGRAMS_MakeFile("LS.COM", ProgramCreate<LS>);
 	PROGRAMS_MakeFile("MEM.COM", ProgramCreate<MEM>);
+	PROGRAMS_MakeFile("MORE.COM", ProgramCreate<MORE>);
 	PROGRAMS_MakeFile("MOUNT.COM", ProgramCreate<MOUNT>);
 	PROGRAMS_MakeFile("RESCAN.COM", ProgramCreate<RESCAN>);
 	PROGRAMS_MakeFile("MIXER.COM", MIXER_ProgramCreate);

src/dos/meson.build

@@ -34,6 +34,7 @@ libdos_sources = files(
     'program_loadrom.cpp',
     'program_ls.cpp',
     'program_mem.cpp',
+    'program_more.cpp',
     'program_mount.cpp',
     'program_mount_common.cpp',
     'program_placeholder.cpp',

src/dos/program_more.cpp

@@ -0,0 +1,164 @@
+/*
+ *  SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ *  Copyright (C) 2022  The DOSBox Staging Team
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#include "program_more.h"
+
+#include "checks.h"
+
+#include "../ints/int10.h"
+
+CHECK_NARROWING();
+
+// ASCII control characters
+static constexpr char char_break           = 0x03;
+static constexpr char char_backspace       = 0x08;
+static constexpr char char_line_feed       = 0x0a;
+static constexpr char char_carriage_return = 0x0d;
+
+void MORE::Run()
+{
+	// Check command line
+
+	if (HelpRequested()) {
+		WriteOut(MSG_Get("SHELL_CMD_MORE_HELP_LONG"));
+		return;
+	}
+
+	if (cmd->GetCount()) {
+		WriteOut(MSG_Get("SHELL_CMD_MORE_SYNTAX"));
+		return;
+	}
+
+	// Prepare screen parameters information
+
+	const uint16_t screen_max_x = INT10_GetTextColumns() - 1;
+	const uint16_t screen_max_y = INT10_GetTextRows() - 1;
+
+	auto get_column = []() {
+		const auto page = real_readb(BIOSMEM_SEG, BIOSMEM_CURRENT_PAGE);
+		return CURSOR_POS_COL(page);
+	};
+
+	// We need to be able to read STDIN for key presses, but it is most
+	// likely redirected - so clone the handle, and reconstruct real STDIN
+	// from STDERR (idea from FreeDOS implementation,
+	// https://github.com/FDOS/more/blob/master/src/more.c)
+
+	uint16_t in_handle = 0;
+	if (!DOS_DuplicateEntry(STDIN, &in_handle) ||
+	    !DOS_ForceDuplicateEntry(STDERR, STDIN)) {
+		LOG_ERR("DOS: Unable to prepare handles in MORE.COM");
+		return;
+	}
+
+	// Main loop
+
+	char character   = '\0';
+	uint16_t amount  = 1;
+	uint16_t counter = 0;
+
+	auto previous_column = get_column();
+	bool previous_was_cr = false; // if last character was 'carriage return'
+	bool previous_was_lf = false; // if last character was 'line feed'
+
+	while (true) {
+		if (!counter)
+			counter = screen_max_y;
+
+		// Read character and duplicate it on the output
+
+		amount = 1;
+		DOS_ReadFile(in_handle, reinterpret_cast<uint8_t *>(&character), &amount);
+		if (!amount)
+			break; // end of stream
+		WriteOut("%c", character);
+
+		// Detect new line; we can't just simply the characters,
+		// as some might be ANSI escape codes
+
+		const auto column = get_column();
+
+		if ((!previous_was_cr && character == char_line_feed) ||
+		    (!previous_was_lf && character == char_carriage_return))
+			--counter; // new line in the input stream
+		else if (character != char_line_feed &&
+		         character != char_carriage_return &&
+		         (!column && (previous_column == screen_max_x)))
+			--counter; // line longer than screen size
+
+		previous_column = column;
+		previous_was_cr = (character == char_carriage_return);
+		previous_was_lf = (character == char_line_feed);
+
+		if (counter)
+			continue;
+
+		// Scrolling occured several times, pause until key press
+
+		if (!column)
+			WriteOut("\n");
+		WriteOut(MSG_Get("SHELL_CMD_PAUSE"));
+
+		amount = 0;
+		while (!amount) {
+			amount = 1;
+			DOS_ReadFile(STDIN,
+			             reinterpret_cast<uint8_t *>(&character),
+			             &amount);
+		}
+
+		// Check for termination by user (CTRL+C)
+
+		if (character == char_break) {
+			WriteOut("^C\n");
+			break;
+		}
+	}
+
+	// End of processing
+
+	WriteOut("\n");
+}
+
+void MORE::AddMessages()
+{
+	MSG_Add("SHELL_CMD_MORE_HELP",
+	        "Display command output or text file one screen at a time.\n");
+	MSG_Add("SHELL_CMD_MORE_HELP_LONG",
+	        "Display command output or text file one screen at a time.\n"
+	        "\n"
+	        "Usage:\n"
+	        "  [color=cyan]COMMAND[reset] | [color=green]more[reset]\n"
+	        "  [color=green]more[reset] < [color=cyan]FILE[reset]\n"
+	        "\n"
+	        "Where:\n"
+	        "  [color=cyan]COMMAND[reset] is the command to diplay output one screen at a time.\n"
+	        "  [color=cyan]FILE[reset]    is the name of the file to display.\n"
+	        "\n"
+	        "Notes:\n"
+	        "  The file must be an exact file name, optionally with a path.\n"
+	        "  This command is only for viewing text files, not binary files.\n"
+	        "\n"
+	        "Examples:\n"
+	        "  [color=cyan]dir /on[reset] | [color=green]more[reset]         ; shows sorted directory content one screen at a time\n"
+	        "  [color=green]more[reset] < [color=cyan]A:\\MANUAL.TXT[reset]   ; displays the file content one screen at a time");
+
+	MSG_Add("SHELL_CMD_MORE_SYNTAX", "Wrong command syntax.");
+}

src/dos/program_more.h

@@ -0,0 +1,42 @@
+/*
+ *  SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ *  Copyright (C) 2022  The DOSBox Staging Team
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#ifndef DOSBOX_PROGRAM_MORE_H
+#define DOSBOX_PROGRAM_MORE_H
+
+#include "programs.h"
+
+class MORE final : public Program {
+public:
+	MORE()
+	{
+		AddMessages();
+		help_detail = {HELP_Filter::All,
+		               HELP_Category::Dosbox,
+		               HELP_CmdType::Program,
+		               "MORE"};
+	}
+	void Run();
+
+private:
+	void AddMessages();
+};
+
+#endif