gpsd/devtools/tablegen.py

#!/usr/bin/env python3
# This code runs compatibly under Python 2 and 3.x for x >= 2.
# Preserve this property!

"""Generate AIS code from text file.

This tool is intended to automate away the drudgery in bring up support
for a new AIS message type.  It parses the tabular description of a message
and generates various useful code snippets from that.  It can also be used to
correct offsets in the tables themselves.

Requires the AIVDM.txt file on standard input. Takes a single argument,
which must match a string in a //: Type comment.  Things you can generate:

* -t: A corrected version of the table.  It will redo all the offsets to be
  in conformance with the bit widths. (The other options rely only on the
  bit widths). If the old and new tables are different, an error message
  describing the corrections will be emitted to standard error.

* -s: A structure definition capturing the message info, with member
  names extracted from the table and types computed from it.

* -c: Bit-extraction code for the AIVDM driver.  Grind out the right sequence
  of UBITS, SBITS, and UCHARS macros, and assignments to structure members,
  guaranteed correct if the table offsets and widths are.

* -d: Code to dump the contents of the unpacked message structure as JSON. If
  the structure has float members, you'll get an if/then/else  guarded by
  the scaled flag.

* -r: A Python initializer stanza for jsongen.py, which is in turn used to
  generate the specification structure for a JSON parse that reads JSON
  into an instance of the message structure.

* -a: Generate all of -s, -d, -c, and -r, and -t, not to stdout but to
  files named with 'tablegen' as a distinguishing part of the stem.
  The stem name can be overridden with the -o option.

This generates almost all the code required to support a new message type.
It's not quite "Look, ma, no handhacking!" You'll need to add default
values to the Python stanza. If the structure definition contains character
arrays, you'll have to fill in the dimensions by hand.  You'll need to add
a bit of glue to ais_json.c so that json_ais_read() actually calls the parser
handing it the specification structure as a control argument.

The -a, -c, -s, -d, and -r modes all take an argument, which should be a
structure reference prefix to be prepended (before a dot) to each fieldname.
Usually you'll need this to look something like "ais->typeN", but it could be
"ais->typeN.FOO" if the generated code has to operate on a union member
inside a type 6 or 8, or something similar.

The -S and -E options allow you to generate code only for a specified span
of fields in the table.  This may be useful for dealing with groups of
messages that have a common head section.

This code interprets magic comments in the input

//: Type
   The token following "Type" is the name of the table
//: xxxx vocabulary
   A subtable describing a controlled vocabulary for field xxxx in the
   preceding table.

TO-DO: generate code for ais.py.
"""

from __future__ import absolute_import, print_function, division

import getopt
import sys


def correct_table(wfp):
    """Writes the corrected table."""
    print("Total bits:", base, file=sys.stderr)
    for (idx, t) in enumerate(table):
        if offsets[idx].strip():
            print("|" + offsets[idx] + t[owidth+1:].rstrip(), file=wfp)
        else:
            print(t.rstrip(), file=wfp)


def make_driver_code(wfp):
    """Writes calls to bit-extraction macros.
    Requires UBITS, SBITS, UCHARS to act as they do in the AIVDM driver.
    Also relies on bitlen to be the message bit length, and i to be
    available as abn index variable."""
    record = after is None
    arrayname = None
    lbase = '\t'
    step = " " * 4
    indent = lbase
    last = 0

    for (i, t) in enumerate(table):
        if '|' in t:
            filds = [s.strip() for s in t.split('|')]
            width = filds[2]
            name = filds[4]
            ftype = filds[5]
            if after == name:
                record = True
                continue
            if before == name:
                record = False
                continue
            if not record:
                continue
            if ftype == 'x':
                print("\t/* skip %s bit%s */" % (width,
                      ["", "s"][width > '1']), file=wfp)
                continue
            if ftype[0] == 'a':
                arrayname = name
                explicit = ftype[1] == '^'
                print('#define ARRAY_BASE %s' % offsets[i].strip(), file=wfp)
                print('#define ELEMENT_SIZE %s' % trailing, file=wfp)
                if explicit:
                    lengthfield = last
                    print(indent + "for (i = 0; i < %s; i++) {" % lengthfield,
                          file=wfp)
                else:
                    lengthfield = "n" + arrayname
                    print(indent + "for (i = 0; ARRAY_BASE + "
                          "(ELEMENT_SIZE*i) < bitlen; i++) {", file=wfp)
                indent += step
                print(indent + "int a = ARRAY_BASE + (ELEMENT_SIZE*i);",
                      file=wfp)
                continue
            offset = offsets[i].split('-')[0]
            if arrayname:
                target = "%s.%s[i].%s" % (structnme, arrayname, name)
                offset = "a + " + offset
            else:
                target = "%s.%s" % (structname, name)
            if ftype[0].lower() in ('u', 'i', 'e'):
                print(indent + "%s\t= %sBITS(%s, %s);" %
                      (target,
                       {'u': 'U', 'e': 'U', 'i': 'S'}[ftype[0].lower()],
                       offset, width), file=wfp)
            elif ftype == 't':
                print(indent + "UCHARS(%s, %s);" % (offset, target), file=wfp)
            elif ftype == 'b':
                print(indent + "%s\t= (bool)UBITS(%s, 1);" % (target, offset),
                      file=wfp)
            else:
                print(indent + "/* %s bits of type %s */" %
                      (width, ftype), file=wfp)
            last = name
    if arrayname:
        indent = lbase
        print(indent + "}", file=wfp)
        if not explicit:
            print(indent + "%s.%s = ind;" %
                  (structname, lengthfield), file=wfp)
        print("#undef ARRAY_BASE", file=wfp)
        print("#undef ELEMENT_SIZE", file=wfp)


def make_structure(wfp):
    """Write a structure definition corresponding to the table."""
    global structname
    record = after is None
    last = 0
    baseindent = 8
    step = 4
    inwards = step
    arrayname = None

    def tabify(n):
        """convert to tabs."""
        return ('\t' * (n // 8)) + (" " * (n % 8))

    print(tabify(baseindent) + "struct {", file=wfp)
    for (i, t) in enumerate(table):
        if '|' in t:
            fields = [s.strip() for s in t.split('|')]
            width = fields[2]
            description = fields[3].strip()
            name = fields[4]
            ftype = fields[5]
            if after == name:
                record = True
                continue
            if before == name:
                record = False
                continue
            if ftype == 'x' or not record:
                continue
            if ftype[0] == 'a':
                arrayname = name
                if ftype[1] == '^':
                    lengthfield = last
                    ftype = ftype[1:]
                else:
                    lengthfield = "n%s" % arrayname
                    print(tabify(baseindent + inwards) +
                          "signed int %s;" % lengthfield, file=wfp)
                if arrayname.endswith("s"):
                    typename = arrayname[:-1]
                else:
                    typename = arrayname
                print(tabify(baseindent + inwards) + "struct %s_t {" %
                      typename, file=wfp)
                inwards += step
                arraydim = ftype[1:]
                continue
            elif ftype == 'u' or ftype == 'e' or ftype[0] == 'U':
                decl = "unsigned int %s;\t/* %s */" % (name, description)
            elif ftype == 'i' or ftype[0] == 'I':
                decl = "signed int %s;\t/* %s */" % (name, description)
            elif ftype == 'b':
                decl = "bool %s;\t/* %s */" % (name, description)
            elif ftype == 't':
                stl = int(width) // 6
                decl = "char %s[%d+1];\t/* %s */" % (name, stl, description)
            else:
                decl = "/* %s bits of type %s */" % (width, ftype)
            print(tabify(baseindent + inwards) + decl, file=wfp)
        last = name
    if arrayname:
        inwards -= step
        print(tabify(baseindent + inwards) + "} %s[%s];"
              % (arrayname, arraydim), file=wfp)
    if "->" in structname:
        typename = structname.split("->")[1]
    if "." in typename:
        structname = structname.split(".")[1]
    print(tabify(baseindent) + "} %s;" % typename, file=wfp)


def make_json_dumper(wfp):
    """Write the skeleton of a JSON dump corresponding to the table.
    Also, if there are subtables, some initializers."""
    last = 0
    if subtables:
        for (name, lines) in subtables:
            wfp.write("    const char *%s_vocabulary[] = {\n" % name)
            for ln in lines:
                value = ln[1]
                if value.endswith(" (default)"):
                    value = value[:-10]
                wfp.write('        "%s",\n' % value)
            wfp.write("    };\n")
            wfp.write('#define DISPLAY_%s(n) (((n) < '
                      '(unsigned int)NITEMS(%s_vocabulary)) ? '
                      '%s_vocabulary[n] : "INVALID %s")\n' %
                      (name.upper(), name, name, name.upper()))
        wfp.write("\n")
    record = after is None
    # Elements of each tuple type except 'a':
    #   1. variable name,
    #   2. unscaled printf format
    #   3. wrapper for unscaled variable reference
    #   4. scaled printf format
    #   5. wrapper for scaled variable reference
    # Elements of 'a' tuple:
    #   1. Name of array field
    #   2. None
    #   3. None
    #   4. None
    #   5. Name of length field
    tuples = []
    vocabularies = [x[0] for x in subtables]
    for (i, t) in enumerate(table):
        if '|' in t:
            fields = [s.strip() for s in t.split('|')]
            name = fields[4]
            ftype = fields[5]
            if after == name:
                record = True
                continue
            if before == name:
                record = False
                continue
            if ftype == 'x' or not record:
                continue
            fmt = r'\"%s\":' % name
            fmt_text = r'\"%s_text\":' % name
            if ftype == 'u':
                tuples.append((name,
                               fmt+"%u", "%s",
                               None, None))
            elif ftype == 'e':
                tuples.append((name,
                               fmt+"%u", "%s",
                               None, None))
                if vocabularies:
                    this = vocabularies.pop(0)
                    ref = "DISPLAY_%s(%%s)" % (this.upper())
                else:
                    ref = 'FOO[%s]'
                tuples.append((name,
                               fmt_text+r"\"%s\"", ref,
                               None, None))
            elif ftype == 'i':
                tuples.append((name,
                               fmt+"%d", "%s",
                               None, None))
            elif ftype == 't':
                tuples.append((name,
                               fmt+r'\"%s\"', "%s",
                               None, None))
            elif ftype == 'b':
                tuples.append((name,
                               fmt+r'\"%s\"', "JSON_BOOL(%s)",
                               None, None))
            elif ftype[0] == 'd':
                print("Cannot generate code for data members", file=sys.stderr)
                sys.exit(1)
            elif ftype[0] == 'U':
                tuples.append((name,
                               fmt+"%u", "%s",
                               fmt+"%%.%sf" % ftype[1], '%s / SCALE'))
            elif ftype[0] == 'I':
                tuples.append((name,
                               fmt+"%d", "%s",
                               fmt+"%%.%sf" % ftype[1], '%s / SCALE'))
            elif ftype[0] == 'a':
                ftype = ftype[1:]
                if ftype[0] == '^':
                    lengthfield = last
                else:
                    lengthfield = "n" + name
                tuples.append((name, None, None, None, lengthfield))
            else:
                print("Unknown type code", ftype, file=sys.stderr)
                sys.exit(1)
        last = name
    startspan = 0

    def scaled(idx):
        """Check if scaled."""
        return tuples[idx][3] is not None

    def tslice(e, idx):
        """Missing docstring."""
        return [x[idx] for x in tuples[startspan:e+1]]

    lbase = " " * 8
    step = " " * 4
    inarray = None
    header = "(void)snprintf(buf + strlen(buf), buflen - strlen(buf),"
    for (i, (var, uf, uv, sf, sv)) in enumerate(tuples):
        if uf is not None:
            print(lbase + "for (i = 0; i < %s.%s; i++) {" % (structname, sv),
                  file=wfp)
            inarray = var
            lbase = " " * 12
            startspan = i+1
            continue
        # At end of tuples, or if scaled flag changes, or if next op is array,
        # flush out dump code for a span of fields.
        if i+1 == len(tuples):
            endit = '}",'
        elif tuples[i+1][1] is not None:
            endit = r',\"%s\":[",' % tuples[i+1][0]
        elif scaled(i) != scaled(i + 1):
            endit = ',",'
        else:
            endit = None
        if endit:
            if not scaled(i):
                print(lbase + header, file=wfp)
                if inarray:
                    prefix = '{"'
                else:
                    prefix = '"'
                print(lbase + step + prefix + ','.join(tslice(i, 1)) + endit,
                      file=wfp)
                for (j, t) in enumerate(tuples[startspan:i+1]):
                    if inarray:
                        ref = structname + "." + inarray + "[i]." + t[0]
                    else:
                        ref = structname + "." + t[0]
                    wfp.write(lbase + step + t[2] % ref)
                    if j == i - startspan:
                        wfp.write(");\n")
                    else:
                        wfp.write(",\n")
            else:
                print(lbase + "if (scaled)", file=wfp)
                print(lbase + step + header, file=wfp)
                print(lbase + step * 2 + '"' + ','.join(tslice(i, 3)) + endit,
                      file=wfp)
                for (j, t) in enumerate(tuples[startspan:i+1]):
                    if inarray:
                        ref = structname + "." + inarray + "[i]." + t[0]
                    else:
                        ref = structname + "." + t[0]
                    wfp.write(lbase + step*2 + t[4] % ref)
                    if j == i - startspan:
                        wfp.write(");\n")
                    else:
                        wfp.write(",\n")
                print(lbase + "else", file=wfp)
                print(lbase + step + header, file=wfp)
                print(lbase + step * 2 + '"' + ','.join(tslice(i, 1)) + endit,
                      file=wfp)
                for (j, t) in enumerate(tuples[startspan:i+1]):
                    if inarray:
                        ref = structname + "." + inarray + "[i]." + t[0]
                    else:
                        ref = structname + "." + t[0]
                    wfp.write(lbase + step*2 + t[2] % ref)
                    if j == i - startspan:
                        wfp.write(");\n")
                    else:
                        wfp.write(",\n")
            startspan = i+1
    # If we were looking at a trailing array, close scope
    if inarray:
        lbase = " " * 8
        print(lbase + "}", file=wfp)
        print(lbase + "if (buf[strlen(buf)-1] == ',')", file=wfp)
        print(lbase + step + r"buf[strlen(buf)-1] = '\0';", file=wfp)
        print(lbase + "(void)strlcat(buf, \"]}\", buflen - strlen(buf));",
              file=wfp)


def make_json_generator(wfp):
    """Write a stanza for jsongen.py.in describing how to generate a
    JSON parser initializer from this table. You need to fill in
    __INITIALIZER__ and default values after this is generated."""
    extra = ""
    last = 0
    arrayname = None
    record = after is None
    print('''\
    {
    "initname" : "__INITIALIZER__",
    "headers": ("AIS_HEADER",),
    "structname": "%s",
    "fieldmap":(
        # fieldname    type        default''' % (structname,), file=wfp)
    for (i, t) in enumerate(table):
        if '|' in t:
            fields = [s.strip() for s in t.split('|')]
            name = fields[4]
            ftype = fields[5]
            if after == name:
                record = True
                continue
            if before == name:
                record = False
                continue
            if ftype == 'x' or not record:
                continue
            if ftype[0] == 'a':
                arrayname = name
                if arrayname.endswith("s"):
                    typename = arrayname[:-1]
                else:
                    typename = arrayname
                readtype = 'array'
                dimension = ftype[1:]
                if dimension[0] == '^':
                    lengthfield = last
                    dimension = dimension[1:]
                else:
                    lengthfield = "n" + arrayname
                extra = " " * 8
                print("        ('%s',%s 'array', (" %
                      (arrayname, " "*(10-len(arrayname))), file=wfp)
                print("            ('%s_t', '%s', (" % (typename, lengthfield),
                      file=wfp)
            else:
                # Depends on the assumption that the read code
                # always sees unscaled JSON.
                readtype = {
                    'u': "uinteger",
                    'U': "uinteger",
                    'e': "uinteger",
                    'i': "integer",
                    'I': "integer",
                    'b': "boolean",
                    't': "string",
                    'd': "string",
                    }[ftype[0]]
                typedefault = {
                    'u': "'PUT_DEFAULT_HERE'",
                    'U': "'PUT_DEFAULT_HERE'",
                    'e': "'PUT DEFAULT HERE'",
                    'i': "'PUT_DEFAULT_HERE'",
                    'I': "'PUT_DEFAULT_HERE'",
                    'b': "\'false\'",
                    't': "None",
                    }[ftype[0]]
                namedefaults = {
                    "month": "'0'",
                    "day": "'0'",
                    "hour": "'24'",
                    "minute": "'60'",
                    "second": "'60'",
                    }
                default = namedefaults.get(name) or typedefault
                print(extra + "        ('%s',%s '%s',%s %s)," %
                      (name, " "*(10-len(name)), readtype,
                       " "*(8-len(readtype)), default), file=wfp)
                if ftype[0] == 'e':
                    print(extra + "        ('%s_text',%s'ignore',   None)," %
                          (name, " "*(6-len(name))), file=wfp)

            last = name
    if arrayname:
        print("                    )))),", file=wfp)
    print("        ),", file=wfp)
    print("    },", file=wfp)


if __name__ == '__main__':
    try:
        # FIXME: Convert to argparse
        (options, arguments) = getopt.getopt(sys.argv[1:], "a:tc:s:d:S:E:r:o:")
    except getopt.GetoptError as msg:
        print("tablecheck.py: " + str(msg))
        raise SystemExit(1)
    generate = maketable = makestruct = makedump = readgen = doall = False
    after = before = None
    filestem = "tablegen"
    for (switch, val) in options:
        if switch == '-a':
            doall = True
            structname = val
        elif switch == '-c':
            generate = True
            structname = val
        elif switch == '-s':
            makestruct = True
            structname = val
        elif switch == '-t':
            maketable = True
        elif switch == '-d':
            makedump = True
            structname = val
        elif switch == '-r':
            readgen = True
            structname = val
        elif switch == '-S':
            after = val
        elif switch == '-E':
            before = val
        elif switch == '-o':
            filestem = val

    if ((not generate and not maketable and not makestruct and
         not makedump and not readgen and not doall)):
        print("tablecheck.py: no mode selected", file=sys.stderr)
        sys.exit(1)

    # First, read in the table.
    # Sets the following:
    #    table - the table lines
    #    widths - array of table widths
    #    ranges - array of table offsets
    #    trailing - bit length of the table or trailing array element
    #    subtables - list of following vocabulary tables.
    tablename = arguments[0]
    table = []
    ranges = []
    subtables = []
    state = 0
    for line in sys.stdin:
        if state == 0 and line.startswith("//: Type") and tablename in line:
            state = 1
            continue
        elif state == 1:		# Found table tag
            if line.startswith("|="):
                state = 2
                continue
        elif state == 2:		# Found table header
            if line.startswith("|="):
                state = 3
                continue
            elif line[0] == '|':
                fields = line.split("|")
                trailing = fields[1]
                ranges.append(fields[1].strip())
                fields[1] = " " * len(fields[1])
                line = "|".join(fields)
            else:
                ranges.append('')
            table.append(line)
            continue
        elif state == 3:		# Found table end
            state = 4
            continue
        elif state == 4:		# Skipping until subsidiary table
            if line.startswith("//:") and "vocabulary" in line:
                subtable_name = line.split()[1]
                subtable_content = []
                state = 5
        elif state == 5:		# Seen subtable header
            if line.startswith("|="):
                state = 6
                continue
        elif state == 6:		# Parsing subtable content
            if line.startswith("|="):
                subtables.append((subtable_name, subtable_content))
                state = 4
                continue
            elif line[0] == '|':
                subtable_content.append(
                    [f.strip() for f in line[1:].strip().split("|")])
            continue
    if state == 0:
        print("Can't find named table.", file=sys.stderr)
        sys.exit(1)
    elif state < 3:
        print("Ill-formed table (in state %d)." % state, file=sys.stderr)
        sys.exit(1)
    table = table[1:]
    ranges = ranges[1:]
    widths = []
    for line in table:
        fields = line.split('|')
        if '|' not in line:        # Continuation line
            widths.append('')
        elif fields[5][0] == 'a':     # Array boundary indicator
            widths.append(None)
        else:
            widths.append(fields[2].strip())
    if '-' in trailing:
        trailing = trailing.split('-')[1]
    trailing = str(int(trailing)+1)

    # Compute offsets for an AIVDM message breakdown, given the bit widths.
    offsets = []
    base = 0
    corrections = False
    for w in widths:
        if w is None:
            offsets.append(repr(base))
            base = 0
        elif w == '':
            offsets.append('')
        else:
            w = int(w)
            offsets.append("%d-%d" % (base, base + w - 1))
            base += w
    if [p for p in zip(ranges, offsets) if p[0] != p[1]]:
        corrections = True
        print("Offset corrections:")
        for (old, new) in zip(ranges, offsets):
            if old != new:
                print(old, "->", new, file=sys.stderr)
    owidth = max(*list(map(len, offsets)))
    for (i, off) in enumerate(offsets):
        offsets[i] += " " * (owidth - len(offsets[i]))

    # Here's where we generate useful output.
    if doall:
        if corrections:
            correct_table(open(filestem + ".txt", "w"))
        make_driver_code(open(filestem + ".c", "w"))
        make_structure(open(filestem + ".h", "w"))
        make_json_dumper(open(filestem + "_json.c", "w"))
        make_json_generator(open(filestem + ".py", "w"))
    elif maketable:
        correct_table(sys.stdout)
    elif generate:
        make_driver_code(sys.stdout)
    elif makestruct:
        make_structure(sys.stdout)
    elif makedump:
        make_json_dumper(sys.stdout)
    elif readgen:
        make_json_generator(sys.stdout)
# end