1 files changed, 89 insertions, 0 deletions
diff --git a/src/expr.c b/src/expr.c
new file mode 100644
index 0000000..ca37ffc
--- /dev/null
+++ b/src/expr.c
@@ -0,0 +1,89 @@
+// Copyright © Tavian Barnes <tavianator@tavianator.com>
+// SPDX-License-Identifier: 0BSD
+
+#include "expr.h"
+
+#include "alloc.h"
+#include "ctx.h"
+#include "diag.h"
+#include "eval.h"
+#include "exec.h"
+#include "list.h"
+#include "printf.h"
+#include "xregex.h"
+
+#include <string.h>
+
+struct bfs_expr *bfs_expr_new(struct bfs_ctx *ctx, bfs_eval_fn *eval_fn, size_t argc, char **argv, enum bfs_kind kind) {
+	bfs_assert(kind != BFS_PATH);
+
+	struct bfs_expr *expr = arena_alloc(&ctx->expr_arena);
+	if (!expr) {
+		return NULL;
+	}
+
+	memset(expr, 0, sizeof(*expr));
+	expr->eval_fn = eval_fn;
+	expr->argc = argc;
+	expr->argv = argv;
+	expr->kind = kind;
+	expr->probability = 0.5;
+	SLIST_PREPEND(&ctx->expr_list, expr, freelist);
+
+	if (bfs_expr_is_parent(expr)) {
+		SLIST_INIT(&expr->children);
+	}
+
+	return expr;
+}
+
+bool bfs_expr_is_parent(const struct bfs_expr *expr) {
+	return expr->eval_fn == eval_and
+		|| expr->eval_fn == eval_or
+		|| expr->eval_fn == eval_not
+		|| expr->eval_fn == eval_comma;
+}
+
+struct bfs_expr *bfs_expr_children(const struct bfs_expr *expr) {
+	if (bfs_expr_is_parent(expr)) {
+		return expr->children.head;
+	} else {
+		return NULL;
+	}
+}
+
+void bfs_expr_append(struct bfs_expr *expr, struct bfs_expr *child) {
+	bfs_assert(bfs_expr_is_parent(expr));
+
+	SLIST_APPEND(&expr->children, child);
+
+	if (!child->pure) {
+		expr->pure = false;
+	}
+
+	expr->persistent_fds += child->persistent_fds;
+	if (expr->ephemeral_fds < child->ephemeral_fds) {
+		expr->ephemeral_fds = child->ephemeral_fds;
+	}
+}
+
+void bfs_expr_extend(struct bfs_expr *expr, struct bfs_exprs *children) {
+	drain_slist (struct bfs_expr, child, children) {
+		bfs_expr_append(expr, child);
+	}
+}
+
+bool bfs_expr_never_returns(const struct bfs_expr *expr) {
+	// Expressions that never return are vacuously both always true and always false
+	return expr->always_true && expr->always_false;
+}
+
+void bfs_expr_clear(struct bfs_expr *expr) {
+	if (expr->eval_fn == eval_exec) {
+		bfs_exec_free(expr->exec);
+	} else if (expr->eval_fn == eval_fprintf) {
+		bfs_printf_free(expr->printf);
+	} else if (expr->eval_fn == eval_regex) {
+		bfs_regfree(expr->regex);
+	}
+}