Allow shebang line in overlays.

Author: sergev

disk.cpp

@@ -35,8 +35,8 @@
 //
 // Open binary image as disk.
 //
-Disk::Disk(Word id, Memory &m, const std::string &p, bool wp)
-    : volume_id(id), memory(m), path(p), write_permit(wp)
+Disk::Disk(Word id, Memory &m, const std::string &p, bool wp, unsigned offset)
+    : volume_id(id), memory(m), path(p), write_permit(wp), file_offset(offset)
 {
     // Open file.
     int open_flag   = write_permit ? O_RDWR : O_RDONLY;
@@ -155,7 +155,8 @@ void Disk::simh_to_memory(unsigned zone, unsigned sector, unsigned addr, unsigne
                              8 +                         // skip OS info
                              (256 * sector);             // sector offset
 
-    if (lseek(file_descriptor, offset_nwords * sizeof(Word), SEEK_SET) < 0)
+    unsigned offset_bytes = offset_nwords * sizeof(Word) + file_offset;
+    if (lseek(file_descriptor, offset_bytes, SEEK_SET) < 0)
         throw std::runtime_error("Disk seek error");
 
     Word *destination = memory.get_ptr(addr);
@@ -186,7 +187,8 @@ void Disk::memory_to_simh(unsigned zone, unsigned sector, unsigned addr, unsigne
                              8 +                         // skip OS info
                              (256 * sector);             // sector offset
 
-    if (lseek(file_descriptor, offset_nwords * sizeof(Word), SEEK_SET) < 0)
+    unsigned offset_bytes = offset_nwords * sizeof(Word) + file_offset;
+    if (lseek(file_descriptor, offset_bytes, SEEK_SET) < 0)
         throw std::runtime_error("Disk seek error");
 
     Word *source   = memory.get_ptr(addr);
@@ -203,7 +205,7 @@ void Disk::file_to_memory(unsigned zone, unsigned sector, unsigned addr, unsigne
     if (zone >= num_zones)
         throw std::runtime_error("Zone number exceeds file size");
 
-    unsigned offset_bytes = (4 * zone + sector) * PAGE_NBYTES / 4;
+    unsigned offset_bytes = (4 * zone + sector) * PAGE_NBYTES / 4 + file_offset;
     if (lseek(file_descriptor, offset_bytes, SEEK_SET) < 0)
         throw std::runtime_error("File seek error");
 
@@ -235,7 +237,7 @@ void Disk::memory_to_file(unsigned zone, unsigned sector, unsigned addr, unsigne
     if (zone >= num_zones)
         throw std::runtime_error("Zone number exceeds file size");
 
-    unsigned offset_bytes = (4 * zone + sector) * PAGE_NBYTES / 4;
+    unsigned offset_bytes = (4 * zone + sector) * PAGE_NBYTES / 4 + file_offset;
     if (lseek(file_descriptor, offset_bytes, SEEK_SET) < 0)
         throw std::runtime_error("File seek error");
 

disk.h

@@ -41,9 +41,12 @@ class Disk {
     int file_descriptor;
     unsigned num_zones;
 
+    // Skip so many bytes at the beginning of the file.
+    unsigned file_offset{};
+
 public:
     // Constructor throws exception if the file cannot be opened.
-    Disk(Word id, Memory &memory, const std::string &path, bool write_permit);
+    Disk(Word id, Memory &memory, const std::string &path, bool write_permit, unsigned offset = 0);
     Disk(Word id, Memory &memory, const std::string &pattern, unsigned num_zones);
 
     // Clone the disk.

machine.cpp

@@ -465,7 +465,7 @@ unsigned Machine::file_search(Word disc_id, Word file_name, bool write_mode)
 // Return error code.
 // In case of success return zero.
 //
-unsigned Machine::file_mount(unsigned disk_unit, unsigned file_index, bool write_mode)
+unsigned Machine::file_mount(unsigned disk_unit, unsigned file_index, bool write_mode, unsigned file_offset)
 {
     if (disk_unit < 030 || disk_unit >= 070)
         throw std::runtime_error("Invalid disk unit " + to_octal(disk_unit) + " in file_mount()");
@@ -492,7 +492,7 @@ unsigned Machine::file_mount(unsigned disk_unit, unsigned file_index, bool write
             return E57_NO_ACCESS;
         }
     }
-    disks[disk_unit - 030] = std::make_unique<Disk>(0, memory, path, write_mode);
+    disks[disk_unit - 030] = std::make_unique<Disk>(0, memory, path, write_mode, file_offset);
     if (bin_created && !write_mode) {
         // Remove binary image of the disk when finished.
         disks[disk_unit - 030]->remove_when_finished();
@@ -768,8 +768,9 @@ void Machine::boot_ms_dubna(const std::string &path)
 
 //
 // Check for binary program (overlay).
+// Return file offset for shebang.
 //
-bool Machine::is_overlay(const std::string &filename)
+bool Machine::is_overlay(const std::string &filename, unsigned *file_offset_ptr)
 {
     // Open binary file.
     std::ifstream file(filename, std::ios_base::binary);
@@ -778,17 +779,33 @@ bool Machine::is_overlay(const std::string &filename)
         return false;
     }
 
+    // Check for shebang line.
+    std::string line(512, '\0');
+    if (!file.read(&line[0], line.size())) {
+        return false;
+    }
+    *file_offset_ptr = 0;
+    if (line[0] == '#' && line[1] == '!') {
+        // Shebang found: determine offset to actual overlay binary.
+        auto newline = line.find('\n');
+        if (newline == std::string::npos) {
+            // Too long line.
+            return false;
+        }
+        *file_offset_ptr = newline + 1;
+    }
+
     // Check file size.
     file.seekg(0, std::ios_base::end);
-    auto nbytes = file.tellg();
+    auto nbytes = file.tellg() - (off_t)*file_offset_ptr;
     if (nbytes / PAGE_NBYTES < 2 || nbytes % PAGE_NBYTES != 0) {
         // Must be a multiple of the page size.
         return false;
     }
 
     // Check magic word OVERLA at fixed offset.
     std::string word(6, '\0');
-    file.seekg(01762 * 6, std::ios_base::beg);
+    file.seekg(01762 * 6 + *file_offset_ptr, std::ios_base::beg);
     if (!file.read(&word[0], word.size())) {
         return false;
     }
@@ -798,7 +815,7 @@ bool Machine::is_overlay(const std::string &filename)
     }
 
     // Check base address of the binary.
-    file.seekg(6, std::ios_base::beg);
+    file.seekg(6 + *file_offset_ptr, std::ios_base::beg);
     if (!file.read(&word[0], word.size())) {
         return false;
     }
@@ -812,7 +829,7 @@ bool Machine::is_overlay(const std::string &filename)
 //
 // Load binary program (overlay).
 //
-void Machine::boot_overlay(const std::string &filename, const std::string &path)
+void Machine::boot_overlay(const std::string &filename, unsigned file_offset, const std::string &path)
 {
     // Mount tape 9/monsys as disk 30, read only.
     disk_search_path = path;
@@ -823,7 +840,7 @@ void Machine::boot_overlay(const std::string &filename, const std::string &path)
 
     // Open overlay as disk 60, read only.
     file_paths.push_back(filename);
-    file_mount(060, file_paths.size(), false);
+    file_mount(060, file_paths.size(), false, file_offset);
 
     // clang-format off
     memory.store(02000, besm6_asm("*70 3000,      utc"));       // читаем таблицу резидентных программ для загрузчика

machine.h

@@ -192,7 +192,7 @@ class Machine {
     unsigned disk_find(Word tape_id);
     void scratch_mount(unsigned disk_unit, unsigned num_zones);
     unsigned file_search(Word disc_id, Word file_name, bool write_mode);
-    unsigned file_mount(unsigned disk_unit, unsigned file_index, bool write_mode);
+    unsigned file_mount(unsigned disk_unit, unsigned file_index, bool write_mode, unsigned file_offset = 0);
 
     // Drum i/o.
     void drum_io(char op, unsigned drum_unit, unsigned zone, unsigned sector, unsigned addr,
@@ -213,10 +213,11 @@ class Machine {
     void print_iso_string(std::ostream &out, unsigned addr);
 
     // Check for binary program (overlay).
-    bool is_overlay(const std::string &filename);
+    // Return file offset for shebang.
+    bool is_overlay(const std::string &filename, unsigned *file_offset_ptr);
 
     // Load binary program (overlay).
-    void boot_overlay(const std::string &filename, const std::string &path = "");
+    void boot_overlay(const std::string &filename, unsigned file_offset, const std::string &path = "");
 
     //
     // Trace methods.

session.cpp

@@ -91,8 +91,9 @@ class Session::Hidden {
     void run()
     {
         try {
-            if (machine.is_overlay(job_file)) {
-                run_overlay();
+            unsigned file_offset{};
+            if (machine.is_overlay(job_file, &file_offset)) {
+                run_overlay(file_offset);
             } else {
                 run_script();
             }
@@ -152,10 +153,10 @@ class Session::Hidden {
     //
     // Run simulation session with given parameters.
     //
-    void run_overlay()
+    void run_overlay(unsigned file_offset)
     {
         // Load binary program.
-        machine.boot_overlay(job_file);
+        machine.boot_overlay(job_file, file_offset);
 
         // Run simulation.
         machine.run();

tests/cli_test.cpp

@@ -179,3 +179,30 @@ TEST(cli, overlay_exe)
 
     EXPECT_EQ(output, " HELLO, ALGOL!\n");
 }
+
+//
+// Run overlay which has shebang line prepended, like "#!/usr/bin/env dubna".
+//
+TEST(cli, shebang_exe)
+{
+    std::string command_line = BUILD_DIR "/dubna " TEST_DIR "/shebang.exe";
+
+    // Set path to the disk images.
+    EXPECT_EQ(setenv("BESM6_PATH", TEST_DIR "/../tapes", 1), 0);
+
+    // Run simulator via shell.
+    FILE *pipe = popen(command_line.c_str(), "r");
+    ASSERT_TRUE(pipe != nullptr);
+
+    // Capture the output as vector of strings.
+    auto output = stream_contents(pipe);
+    std::cout << output;
+
+    // Check exit code.
+    int exit_status = pclose(pipe);
+    int exit_code   = WEXITSTATUS(exit_status);
+    ASSERT_NE(exit_status, -1);
+    ASSERT_EQ(exit_code, 0);
+
+    EXPECT_EQ(output, " HELLO, ALGOL!\n");
+}