Add brainf interpreter (#58)

1 files changed, 90 insertions, 0 deletions

diff --git a/homework/81270/brainf-interpret/Interpreter.cpp b/homework/81270/brainf-interpret/Interpreter.cpp
new file mode 100644
index 0000000..ebca77b
--- /dev/null
+++ b/homework/81270/brainf-interpret/Interpreter.cpp
@@ -0,0 +1,90 @@
+//
+// Created by bmestanov on 15.11.18.
+//
+
+#define TAPE_SIZE 65536
+#define STACK_SIZE 8192
+
+#include <fstream>
+#include <iostream>
+
+void failIf(bool condition, const char *message) {
+    if (condition) {
+        std::cerr << message;
+        exit(1);
+    }
+}
+
+int main(int argc, char **argv) {
+    argc--;
+    argv++;
+    char memory[TAPE_SIZE] = {0};
+    char *pp = memory; // program pointer
+    long stack[STACK_SIZE];
+    int sp = 0; // stack pointer
+
+    failIf(!argv[0], "No file provided");
+
+    std::ifstream file;
+    file.open(argv[0]);
+
+    failIf(!file, "Error opening file");
+
+    while (!file.eof()) {
+        auto symbol = static_cast<char>(file.get());
+        switch (symbol) {
+            case '>': {
+                // Allow memory wrap
+                pp = memory + (pp - memory + 1) % TAPE_SIZE;
+                break;
+            }
+            case '<': {
+                pp = memory + (pp - memory - 1) % TAPE_SIZE;
+                break;
+            }
+            case '+': {
+                (*pp)++;
+                break;
+            }
+            case '-': {
+                (*pp)--;
+                break;
+            }
+            case '.': {
+                std::putchar(*pp);
+                break;
+            }
+            case ',': {
+                *pp = static_cast<char>(std::getchar());
+                break;
+            }
+            case '[': {
+                if (*pp) {
+                    failIf(sp == STACK_SIZE, "Stack overflow");
+                    stack[sp++] = file.tellg();
+                } else {
+                    long move = 1;
+                    while (move > 0) {
+                        auto next = static_cast<char>(file.get());
+                        if (next == '[') move++;
+                        if (next == ']') move--;
+                        if (file.eof()) failIf(true, "Invalid syntax");
+                    }
+                }
+                break;
+            }
+            case ']': {
+                failIf(sp == 0, "Invalid syntax");
+                if (*pp) {
+                    long top = stack[sp - 1];
+                    file.seekg(top);
+                } else {
+                    sp--;
+                }
+            }
+            default:;
+        }
+    }
+
+    return 0;
+}
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