feat: implement environment table for vm

include/vm/fzl_vm.h

@@ -5,6 +5,7 @@
 #include <compiler/utils/fzl_const_pool.h> // NOTE: move outside compiler scope to common
 #include <stddef.h>
 #include <stdint.h>
+#include <vm/fzl_vm_env.h>
 
 // VM descriptor
 typedef struct
@@ -26,7 +27,8 @@ typedef struct
   size_t ctop;
 
   // Environment stack
-  // TODO: implement `estack` and `etop`
+  fzl_vm_env_t estack[256];
+  size_t etop;
 } fzl_vm_t;
 
 // Allocate FZL VM

include/vm/fzl_vm_env.h

@@ -0,0 +1,52 @@
+#ifndef FZL_VM_ENV_H
+#define FZL_VM_ENV_H
+
+#include <common/fzl_value.h>
+#include <stdbool.h>
+#include <stddef.h>
+
+typedef enum
+{
+  FZL_VM_ENV_WRESULT_OK,
+  FZL_VM_ENV_WRESULT_ERR,
+  FZL_VM_ENV_WRESULT_ERR_EXISTS,
+  FZL_VM_ENV_WRESULT_ERR_NOT_FOUND
+} fzl_vm_env_wresult_t;
+
+// Environment table entry descriptor
+typedef struct
+{
+  char *name;
+  fzl_value_t value;
+} fzl_vm_env_entry_t;
+
+// Environment table descriptor
+typedef struct
+{
+  size_t size;
+  size_t remainder;
+
+  fzl_vm_env_entry_t *table;
+} fzl_vm_env_t;
+
+// Allocate env table
+fzl_vm_env_t *fzl_mkenv();
+
+// Try get value by name
+fzl_value_t fzl_env_lookup(fzl_vm_env_t *env, char *name);
+
+// Check name in env table
+bool fzl_env_contains(fzl_vm_env_t *env, char *name);
+
+// Store new value
+fzl_vm_env_wresult_t fzl_env_storevalue(fzl_vm_env_t *env, char *name,
+                                        fzl_value_t val);
+
+// Overwrite existing value
+fzl_vm_env_wresult_t fzl_env_writevalue(fzl_vm_env_t *env, char *name,
+                                        fzl_value_t newval);
+
+// Free env table
+void fzl_freeenv(fzl_vm_env_t *env);
+
+#endif // FZL_VM_ENV_H