Minibox: Add a somewhat improved shell

This shell actually lexes and produces a AST which makes it easier to
add features and will makes it more difficult to introduce bugs. So
basically it is just better code.

1 files changed, 99 insertions, 0 deletions

diff --git a/userland/minibox/utilities/sh/ast.c b/userland/minibox/utilities/sh/ast.c
new file mode 100644
index 0000000..64dd725
--- /dev/null
+++ b/userland/minibox/utilities/sh/ast.c
@@ -0,0 +1,99 @@
+#include "ast.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+void free_ast_command(struct AST *ast) {
+  free_ast(ast->children);
+  free_ast(ast->pipe_rhs);
+}
+
+void free_ast(struct AST *ast) {
+  for (; ast;) {
+    if (AST_COMMAND == ast->type)
+      free_ast_command(ast);
+    struct AST *old = ast;
+    ast = ast->next;
+    free(old);
+  }
+}
+
+struct AST *allocate_ast(void) {
+  struct AST *r = malloc(sizeof(struct AST));
+  memset(r, 0, sizeof(struct AST));
+  return r;
+}
+
+int parse_command(struct TOKEN **token_ptr, struct AST *cur) {
+  struct TOKEN *token = *token_ptr;
+  if (TOKEN_CHARS != token->type)
+    return 0;
+  cur->type = AST_COMMAND;
+  cur->val.type = AST_VALUE_STRING;
+  cur->val.string = token->string_rep;
+  // Parse the arguments
+  if (token->next && TOKEN_CHARS == token->next->type) {
+    token = token->next;
+    cur->children = allocate_ast();
+    struct AST *child = cur->children;
+    for (;;) {
+      child->type = AST_EXPRESSION;
+      child->val.type = AST_VALUE_STRING;
+      child->val.string = token->string_rep;
+      if (!token->next)
+        break;
+      if (TOKEN_CHARS != token->next->type)
+        break;
+      token = token->next;
+      child->next = allocate_ast();
+      child = child->next;
+    }
+  }
+  token = token->next;
+  // Parse the stream modifier "prog > file.txt"
+  if (token &&
+      (TOKEN_STREAM == token->type || TOKEN_STREAM_APPEND == token->type)) {
+    cur->file_out_append = (TOKEN_STREAM_APPEND == token->type);
+    // TODO: Allow it to be modified
+    cur->file_out_fd_to_use = STDOUT_FILENO;
+    token = token->next;
+    cur->file_out = token->string_rep;
+    token = token->next;
+  }
+  // Parse pipe '|'
+  if (token && TOKEN_PIPE == token->type) {
+    cur->pipe_rhs = allocate_ast();
+    token = token->next;
+    if (!parse_command(&token, cur->pipe_rhs)) {
+      fprintf(stderr, "Expected command after |.");
+      exit(1);
+    }
+  }
+  *token_ptr = token;
+  return 1;
+}
+
+struct AST *generate_ast(struct TOKEN *token) {
+  struct AST *head = NULL;
+  struct AST *prev = NULL;
+  for (; token;) {
+    struct AST *cur = allocate_ast();
+    if (prev)
+      prev->next = cur;
+    if (parse_command(&token, cur)) {
+    } else if (TOKEN_AND == token->type) {
+      cur->type = AST_CONDITIONAL_AND;
+      token = token->next;
+    } else if (TOKEN_NOT == token->type) {
+      cur->type = AST_CONDITIONAL_NOT;
+      token = token->next;
+    } else {
+      token = token->next;
+    }
+    if (!head)
+      head = cur;
+    prev = cur;
+  }
+  return head;
+}