C codegen: preparations for different seq and string implementations

compiler/ccgliterals.nim

@@ -0,0 +1,81 @@
+#
+#
+#           The Nim Compiler
+#        (c) Copyright 2018 Andreas Rumpf
+#
+#    See the file "copying.txt", included in this
+#    distribution, for details about the copyright.
+#
+
+## This include file contains the logic to produce constant string
+## and seq literals. The code here is responsible that
+## ``const x = ["a", "b"]`` works without hidden runtime creation code.
+## The price is that seqs and strings are not purely a library
+## implementation.
+
+template detectVersion(field, corename) =
+  if m.g.field == 0:
+    let core = getCompilerProc(corename)
+    if core == nil or core.kind != skConst:
+      m.g.field = 1
+    else:
+      m.g.field = int ast.getInt(core.ast)
+  result = m.g.field
+
+proc detectStrVersion(m: BModule): int =
+  detectVersion(strVersion, "nimStrVersion")
+
+proc detectSeqVersion(m: BModule): int =
+  detectVersion(seqVersion, "nimSeqVersion")
+
+# ----- Version 1: GC'ed strings and seqs --------------------------------
+
+proc genStringLiteralDataOnlyV1(m: BModule, s: string): Rope =
+  discard cgsym(m, "TGenericSeq")
+  result = getTempName(m)
+  addf(m.s[cfsData], "STRING_LITERAL($1, $2, $3);$n",
+       [result, makeCString(s), rope(len(s))])
+
+proc genStringLiteralV1(m: BModule; n: PNode): Rope =
+  if s.isNil:
+    result = ropecg(m, "((#NimStringDesc*) NIM_NIL)", [])
+  else:
+    let id = nodeTableTestOrSet(m.dataCache, n, m.labels)
+    if id == m.labels:
+      # string literal not found in the cache:
+      result = ropecg(m, "((#NimStringDesc*) &$1)",
+                      [genStringLiteralDataOnlyV1(m, n.strVal)])
+    else:
+      result = ropecg(m, "((#NimStringDesc*) &$1$2)",
+                      [m.tmpBase, rope(id)])
+
+# ------ Version 2: destructor based strings and seqs -----------------------
+
+proc genStringLiteralDataOnlyV2(m: BModule, s: string): Rope =
+  discard "to implement"
+
+proc genStringLiteralV2(m: BModule; n: PNode): Rope =
+  discard "to implement"
+
+# ------ Version selector ---------------------------------------------------
+
+proc genStringLiteralDataOnly(m: BModule; s: string; info: TLineInfo): Rope =
+  case detectStrVersion(m)
+  of 0, 1: result = genStringLiteralDataOnlyV1(m, s)
+  of 2: result = genStringLiteralDataOnlyV2(m, s)
+  else:
+    localError(info, "cannot determine how to produce code for string literal")
+
+proc genStringLiteralFromData(m: BModule; data: Rope; info: TLineInfo): Rope =
+  result = ropecg(m, "((#NimStringDesc*) &$1)",
+                [data])
+
+proc genNilStringLiteral(m: BModule; info: TLineInfo): Rope =
+  result = ropecg(m, "((#NimStringDesc*) NIM_NIL)", [])
+
+proc genStringLiteral(m: BModule; n: PNode): Rope =
+  case detectStrVersion(m)
+  of 0, 1: result = genStringLiteralV1(m, n)
+  of 2: result = genStringLiteralV2(m, n)
+  else:
+    localError(n.info, "cannot determine how to produce code for string literal")