Add boolean generator expressions

Add generator expressions that combine and use boolean test results:

 $<0:...>         = empty string (ignores "...")
 $<1:...>         = content of "..."
 $<AND:?[,?]...>  = '1' if all '?' are '1', else '0'
 $<OR:?[,?]...>   = '0' if all '?' are '0', else '1'
 $<NOT:?>         = '0' if '?' is '1', else '1'

These will be useful to evaluate (future) boolean query expressions and
condition content on the results.  Include tests and documentation.

2 files changed, 55 insertions, 1 deletions

diff --git a/Source/cmDocumentGeneratorExpressions.h b/Source/cmDocumentGeneratorExpressions.h
index 5359013..5d6553d 100644
--- a/Source/cmDocumentGeneratorExpressions.h
+++ b/Source/cmDocumentGeneratorExpressions.h
@@ -16,6 +16,8 @@
   "Generator expressions are evaluted during build system generation "  \
   "to produce information specific to each build configuration.  "      \
   "Valid expressions are:\n"                                            \
+  "  $<0:...>                  = empty string (ignores \"...\")\n"      \
+  "  $<1:...>                  = content of \"...\"\n"                  \
   "  $<CONFIGURATION>          = configuration name\n"                  \
   "  $<TARGET_FILE:tgt>        = main file (.exe, .so.1.2, .a)\n"       \
   "  $<TARGET_LINKER_FILE:tgt> = file used to link (.a, .lib, .so)\n"   \
@@ -25,6 +27,12 @@
   "versions can produce the directory and file name components:\n"      \
   "  $<TARGET_FILE_DIR:tgt>/$<TARGET_FILE_NAME:tgt>\n"                  \
   "  $<TARGET_LINKER_FILE_DIR:tgt>/$<TARGET_LINKER_FILE_NAME:tgt>\n"    \
-  "  $<TARGET_SONAME_FILE_DIR:tgt>/$<TARGET_SONAME_FILE_NAME:tgt>\n"
+  "  $<TARGET_SONAME_FILE_DIR:tgt>/$<TARGET_SONAME_FILE_NAME:tgt>\n"    \
+  "Boolean expressions:\n"                                              \
+  "  $<AND:?[,?]...>           = '1' if all '?' are '1', else '0'\n"    \
+  "  $<OR:?[,?]...>            = '0' if all '?' are '0', else '1'\n"    \
+  "  $<NOT:?>                  = '0' if '?' is '1', else '1'\n"         \
+  "where '?' is always either '0' or '1'.\n"                            \
+  ""
 
 #endif
diff --git a/Source/cmGeneratorExpression.cxx b/Source/cmGeneratorExpression.cxx
index f88ab0b..ed33c7e 100644
--- a/Source/cmGeneratorExpression.cxx
+++ b/Source/cmGeneratorExpression.cxx
@@ -103,6 +103,26 @@ bool cmGeneratorExpression::Evaluate()
 }
 
 //----------------------------------------------------------------------------
+static bool cmGeneratorExpressionBool(const char* c, std::string& result,
+                                      const char* name,
+                                      const char* a, const char* b)
+{
+  result = a;
+  while((c[0] == '0' || c[0] == '1') && (c[1] == ',' || c[1] == '>'))
+    {
+    if(c[0] == b[0]) { result = b; }
+    c += 2;
+    }
+  if(c[0])
+    {
+    result = name;
+    result += " requires one or more comma-separated '0' or '1' values.";
+    return false;
+    }
+  return true;
+}
+
+//----------------------------------------------------------------------------
 bool cmGeneratorExpression::Evaluate(const char* expr, std::string& result)
 {
   if(this->TargetInfo.find(expr))
@@ -116,6 +136,32 @@ bool cmGeneratorExpression::Evaluate(const char* expr, std::string& result)
     {
     result = this->Config? this->Config : "";
     }
+  else if(strncmp(expr, "$<0:",4) == 0)
+    {
+    result = "";
+    }
+  else if(strncmp(expr, "$<1:",4) == 0)
+    {
+    result = std::string(expr+4, strlen(expr)-5);
+    }
+  else if(strncmp(expr, "$<NOT:",6) == 0)
+    {
+    const char* c = expr+6;
+    if((c[0] != '0' && c[0] != '1') || c[1] != '>' || c[2])
+      {
+      result = "NOT requires exactly one '0' or '1' value.";
+      return false;
+      }
+    result = c[0] == '1'? "0" : "1";
+    }
+  else if(strncmp(expr, "$<AND:",6) == 0)
+    {
+    return cmGeneratorExpressionBool(expr+6, result, "AND", "1", "0");
+    }
+  else if(strncmp(expr, "$<OR:",5) == 0)
+    {
+    return cmGeneratorExpressionBool(expr+5, result, "OR", "0", "1");
+    }
   else
     {
     result = "Expression syntax not recognized.";