kconfig: add built-in function support

This commit adds a new concept 'function' to do more text processing
in Kconfig.

A function call looks like this:

  $(function,arg1,arg2,arg3,...)

This commit adds the basic infrastructure to expand functions.
Change the text expansion helpers to take arguments.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

1 files changed, 130 insertions, 12 deletions

diff --git a/scripts/kconfig/preprocess.c b/scripts/kconfig/preprocess.c
index a2eb2eb02929..f32a496626da 100644
--- a/scripts/kconfig/preprocess.c
+++ b/scripts/kconfig/preprocess.c
@@ -10,6 +10,10 @@
 
 #include "list.h"
 
+#define ARRAY_SIZE(arr)         (sizeof(arr) / sizeof((arr)[0]))
+
+static char *expand_string_with_args(const char *in, int argc, char *argv[]);
+
 static void __attribute__((noreturn)) pperror(const char *format, ...)
 {
         va_list ap;
@@ -92,20 +96,123 @@ void env_write_dep(FILE *f, const char *autoconfig_name)
         }
 }
 
-static char *eval_clause(const char *str, size_t len)
+/*
+ * Built-in functions
+ */
+struct function {
+        const char *name;
+        unsigned int min_args;
+        unsigned int max_args;
+        char *(*func)(int argc, char *argv[]);
+};
+
+static const struct function function_table[] = {
+        /* Name         MIN     MAX     Function */
+};
+
+#define FUNCTION_MAX_ARGS               16
+
+static char *function_expand(const char *name, int argc, char *argv[])
 {
-        char *tmp, *name, *res;
+        const struct function *f;
+        int i;
+
+        for (i = 0; i < ARRAY_SIZE(function_table); i++) {
+                f = &function_table[i];
+                if (strcmp(f->name, name))
+                        continue;
+
+                if (argc < f->min_args)
+                        pperror("too few function arguments passed to '%s'",
+                                name);
+
+                if (argc > f->max_args)
+                        pperror("too many function arguments passed to '%s'",
+                                name);
+
+                return f->func(argc, argv);
+        }
+
+        return NULL;
+}
+
+/*
+ * Evaluate a clause with arguments.  argc/argv are arguments from the upper
+ * function call.
+ *
+ * Returned string must be freed when done
+ */
+static char *eval_clause(const char *str, size_t len, int argc, char *argv[])
+{
+        char *tmp, *name, *res, *prev, *p;
+        int new_argc = 0;
+        char *new_argv[FUNCTION_MAX_ARGS];
+        int nest = 0;
+        int i;
 
         tmp = xstrndup(str, len);
 
-        name = expand_string(tmp);
+        prev = p = tmp;
+
+        /*
+         * Split into tokens
+         * The function name and arguments are separated by a comma.
+         * For example, if the function call is like this:
+         *   $(foo,$(x),$(y))
+         *
+         * The input string for this helper should be:
+         *   foo,$(x),$(y)
+         *
+         * and split into:
+         *   new_argv[0] = 'foo'
+         *   new_argv[1] = '$(x)'
+         *   new_argv[2] = '$(y)'
+         */
+        while (*p) {
+                if (nest == 0 && *p == ',') {
+                        *p = 0;
+                        if (new_argc >= FUNCTION_MAX_ARGS)
+                                pperror("too many function arguments");
+                        new_argv[new_argc++] = prev;
+                        prev = p + 1;
+                } else if (*p == '(') {
+                        nest++;
+                } else if (*p == ')') {
+                        nest--;
+                }
 
-        res = env_expand(name);
+                p++;
+        }
+        new_argv[new_argc++] = prev;
+
+        /*
+         * Shift arguments
+         * new_argv[0] represents a function name or a variable name.  Put it
+         * into 'name', then shift the rest of the arguments.  This simplifies
+         * 'const' handling.
+         */
+        name = expand_string_with_args(new_argv[0], argc, argv);
+        new_argc--;
+        for (i = 0; i < new_argc; i++)
+                new_argv[i] = expand_string_with_args(new_argv[i + 1],
+                                                      argc, argv);
+
+        /* Look for built-in functions */
+        res = function_expand(name, new_argc, new_argv);
         if (res)
                 goto free;
 
+        /* Last, try environment variable */
+        if (new_argc == 0) {
+                res = env_expand(name);
+                if (res)
+                        goto free;
+        }
+
         res = xstrdup("");
 free:
+        for (i = 0; i < new_argc; i++)
+                free(new_argv[i]);
         free(name);
         free(tmp);
 
@@ -124,14 +231,14 @@ free:
  * after the corresponding closing parenthesis, in this case, *str will be
  *     $(BAR)
  */
-char *expand_dollar(const char **str)
+static char *expand_dollar_with_args(const char **str, int argc, char *argv[])
 {
         const char *p = *str;
         const char *q;
         int nest = 0;
 
         /*
-         * In Kconfig, variable references always start with "$(".
+         * In Kconfig, variable/function references always start with "$(".
          * Neither single-letter variables as in $A nor curly braces as in ${CC}
          * are supported.  '$' not followed by '(' loses its special meaning.
          */
@@ -158,10 +265,16 @@ char *expand_dollar(const char **str)
         /* Advance 'str' to after the expanded initial portion of the string */
         *str = q + 1;
 
-        return eval_clause(p, q - p);
+        return eval_clause(p, q - p, argc, argv);
+}
+
+char *expand_dollar(const char **str)
+{
+        return expand_dollar_with_args(str, 0, NULL);
 }
 
-static char *__expand_string(const char **str, bool (*is_end)(char c))
+static char *__expand_string(const char **str, bool (*is_end)(char c),
+                             int argc, char *argv[])
 {
         const char *in, *p;
         char *expansion, *out;
@@ -177,7 +290,7 @@ static char *__expand_string(const char **str, bool (*is_end)(char c))
                 if (*p == '$') {
                         in_len = p - in;
                         p++;
-                        expansion = expand_dollar(&p);
+                        expansion = expand_dollar_with_args(&p, argc, argv);
                         out_len += in_len + strlen(expansion);
                         out = xrealloc(out, out_len);
                         strncat(out, in, in_len);
@@ -210,13 +323,18 @@ static bool is_end_of_str(char c)
 }
 
 /*
- * Expand variables in the given string.  Undefined variables
+ * Expand variables and functions in the given string.  Undefined variables
  * expand to an empty string.
  * The returned string must be freed when done.
  */
+static char *expand_string_with_args(const char *in, int argc, char *argv[])
+{
+        return __expand_string(&in, is_end_of_str, argc, argv);
+}
+
 char *expand_string(const char *in)
 {
-        return __expand_string(&in, is_end_of_str);
+        return expand_string_with_args(in, 0, NULL);
 }
 
 static bool is_end_of_token(char c)
@@ -234,5 +352,5 @@ static bool is_end_of_token(char c)
  */
 char *expand_one_token(const char **str)
 {
-        return __expand_string(str, is_end_of_token);
+        return __expand_string(str, is_end_of_token, 0, NULL);
 }