Proof of concept for JSON parder generation.

1 files changed, 89 insertions, 0 deletions

diff --git a/jsongen.py b/jsongen.py
new file mode 100755
index 00000000..d684b6fb
--- /dev/null
+++ b/jsongen.py
@@ -0,0 +1,89 @@
+#!/usr/bin/env python
+#
+# Never hand-hack what you can generate...
+#
+# This code senerate template declarations for AIS-JSON parsing from a
+# declarative specification of a JSON structure - and generate those
+# declarative specification from the Python format strings for
+# dumping the structures
+#
+import sys, getopt
+
+# Make shared field names to data types 
+typemap = {
+    # AIS fields
+    "raim":"boolean",
+    "accuracy":"boolean",
+    "timestamp":"string",
+    }
+
+# Map C and Python-type format letters to JSON parser datatypes 
+fmtmap = {
+    "d": "integer",
+    "u": "uinteger",
+    "f": "real",
+    "a": "string",
+    }
+
+
+ais_specs = (
+    ("json_ais4", "\tAIS_HEADER,", "ais->type4",
+     "\"timestamp\":\"%4u:%02u:%02uT%02u:%02u:%02uZ\","\
+     "\"accuracy\":%s,\"lon\":%d,\"lat\":%d,"\
+     "\"epfd\":%u,\"raim\":%s,\"radio\":%d}\r\n"
+     ),
+    )
+    
+def generate(initname, header, structname, specifier):
+    specifier = specifier.strip()
+    if specifier[-1] == "}":
+        specifier = specifier[:-1]
+    else:
+        print "Missing terminating }"
+        sys.exit(1)
+
+    print "    const struct json_attr_t %s[] = {" % initname
+    if header:
+        print header
+    for item in specifier.split(","):
+        if "timestamp" in item:
+            (attr, itype) = ("timestamp", "string")
+        else:
+            itype = None
+            (attr, fmt) = item.split(":")
+            if attr[0] == '"':
+                attr = attr[1:]
+            if attr[-1] == '"':
+                attr = attr[:-1]
+            if attr in typemap:
+                itype = typemap[attr]
+            if fmt[-1] in fmtmap:
+                itype = fmtmap[fmt[-1]]
+        if itype == "string":
+            deref = ""
+        else:
+            deref = "&"
+        print '\t{"%s",%s%s,%s.addr.%s = %s%s.%s,' % \
+               (attr, " "*(12-len(attr)),itype, " "*(12-len(itype)), itype, deref, structname, attr)
+        leader = " " * 37
+        if itype == "string":
+            print leader + ".maxlen = sizeof(%s.%s)}," % (structname, attr)
+        elif itype == "boolean":
+            print leader + ".dflt.boolean = false},"
+        elif itype == "real":
+            print leader + ".dflt.real = 0.0},"
+        else:
+            print leader + ".dflt.%s = 0}," % itype
+
+    print """\
+	{NULL},
+    };
+
+"""
+
+if __name__ == '__main__':
+    for description in ais_specs:
+        generate(initname=description[0],
+                 header=description[1],
+                 structname=description[2],
+                 specifier=description[3])