1 files changed, 79 insertions, 0 deletions
diff --git a/tools/glsl_preproc/variables.py b/tools/glsl_preproc/variables.py
new file mode 100644
index 0000000..187fd79
--- /dev/null
+++ b/tools/glsl_preproc/variables.py
@@ -0,0 +1,79 @@
+import re
+
+def slugify(value):
+    value = re.sub(r'[^\w]+', '_', value.lower()).strip('_')
+    if value[:1].isdigit():
+        value = '_' + value
+    return value
+
+# A single variable (enclosed by the template)
+class Var(object):
+    STRUCT_NAME = 'vars'
+    CSIZES = {
+        # This array doesn't have to be exact, it's only used for sorting
+        # struct members to save a few bytes of memory here and there
+        'int':      4,
+        'unsigned': 4,
+        'float':    4,
+        'ident_t':  2,
+        'uint8_t':  1,
+        'bool':     1,
+    }
+
+    def __init__(self, ctype, expr, name, csize=0, linenr=0):
+        self.ctype  = ctype
+        self.csize  = csize or Var.CSIZES[ctype]
+        self.expr   = expr
+        self.name   = name
+        self.linenr = linenr
+
+    def __str__(self):
+        return f'{Var.STRUCT_NAME}.{self.name}'
+
+def is_literal(expr):
+    return expr.isnumeric() or expr in ['true', 'false']
+
+# A (deduplicated) set of variables
+class VarSet(object):
+    def __init__(self):
+        self.varmap = {} # expr -> cvar
+
+    def __iter__(self):
+        # Sort from largest to smallest variable to optimize struct padding
+        yield from sorted(self.varmap.values(),
+            reverse=True,
+            key=lambda v: v.csize,
+        )
+
+    def __bool__(self):
+        return True if self.varmap else False
+
+    def add_var_raw(self, var):
+        # Re-use existing entry for identical expression/type pairs
+        if old := self.varmap.get(var.expr):
+            if var.ctype != old.ctype:
+                raise SyntaxError(f'Conflicting types for expression {var.expr}, '
+                                  f'got {var.ctype}, expected {old.ctype}')
+            assert old.name == var.name
+            return old
+
+        names = [ v.name for v in self.varmap.values() ]
+        while var.name in names:
+            var.name += '_'
+        self.varmap[var.expr] = var
+        return var
+
+    # Returns the added variable
+    def add_var(self, ctype, expr, name=None, linenr=0):
+        assert expr
+        expr = expr.strip()
+        if is_literal(expr):
+            return expr
+        name = name or slugify(expr)
+
+        var = Var(ctype, expr=expr, name=name, linenr=linenr)
+        return self.add_var_raw(var)
+
+    def merge(self, other):
+        for var in other:
+            self.add_var_raw(var)