add file_getprop() to updater

Add a function to read a property from a ".prop"-formatted file
(key=value pairs, one per line, ignore # comment lines and blank
lines).  Move ErrorAbort to the core of edify; it's not specific to
updater now that errors aren't stored in the app cookie.

2 files changed, 17 insertions, 0 deletions

diff --git a/edify/expr.c b/edify/expr.c
index f1c5555..72e5100 100644
--- a/edify/expr.c
+++ b/edify/expr.c
@@ -417,3 +417,16 @@ char** ReadVarArgs(State* state, int argc, Expr* argv[]) {
     }
     return args;
 }
+
+// Use printf-style arguments to compose an error message to put into
+// *state.  Returns NULL.
+char* ErrorAbort(State* state, char* format, ...) {
+    char* buffer = malloc(4096);
+    va_list v;
+    va_start(v, format);
+    vsnprintf(buffer, 4096, format, v);
+    va_end(v);
+    free(state->errmsg);
+    state->errmsg = buffer;
+    return NULL;
+}
diff --git a/edify/expr.h b/edify/expr.h
index 671b499..d2e7392 100644
--- a/edify/expr.h
+++ b/edify/expr.h
@@ -118,5 +118,9 @@ int ReadArgs(State* state, Expr* argv[], int count, ...);
 // strings it contains.
 char** ReadVarArgs(State* state, int argc, Expr* argv[]);
 
+// Use printf-style arguments to compose an error message to put into
+// *state.  Returns NULL.
+char* ErrorAbort(State* state, char* format, ...);
+
 
 #endif  // _EXPRESSION_H