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| 1 | +Dis Virtual Machine Tools for Python |
| 2 | +==================================== |
| 3 | + |
| 4 | +Introduction |
| 5 | +------------ |
| 6 | + |
| 7 | +This package contains Python modules for reading and writing files for the Dis |
| 8 | +virtual machine[1], used by the Inferno operating system[2]. Although the aim |
| 9 | +of these modules was to create a toolchain for producing .dis files, they are |
| 10 | +more useful for reading existing ones. |
| 11 | + |
| 12 | +Reading a .dis File |
| 13 | +------------------- |
| 14 | + |
| 15 | +Sample .dis files are not provided, but you can compile the Limbo source code |
| 16 | +files from the Tests/Limbo directory to obtain simple .dis files to inspect. |
| 17 | +This is done using the limbo compiler supplied with Inferno. |
| 18 | + |
| 19 | +From within the package directory, or with the directory on the PYTHONPATH, |
| 20 | +you can run the Python interpreter and inspect the contents of an existing .dis |
| 21 | +file in the following way: |
| 22 | + |
| 23 | + import dis |
| 24 | + d = dis.Dis() |
| 25 | + d.read(open("/tmp/countmin.dis"), "countmin.dis") |
| 26 | + d.list() |
| 27 | + |
| 28 | +For the compiled version of the countmin.b file, the Python should produce |
| 29 | +output similar to the following: |
| 30 | + |
| 31 | + 0x0: load 0(mp), $0x0, 48(fp) |
| 32 | + 0x1: movw $0x0, 40(fp) |
| 33 | + 0x2: blew $0x7b, 40(fp), $0x5 |
| 34 | + 0x3: addw $0x1, 40(fp) |
| 35 | + 0x4: jmp $0x2 |
| 36 | + 0x5: ret |
| 37 | + |
| 38 | + entry 0x0, 1 |
| 39 | + desc $0x0, 8, "c0" |
| 40 | + desc $0x1, 56, "00c8" |
| 41 | + |
| 42 | + var @mp, 8 |
| 43 | + string @mp+0, "$Sys" |
| 44 | + |
| 45 | + module count |
| 46 | + |
| 47 | + link 0x0, 1, 0x4244b354, "init" |
| 48 | + |
| 49 | + ldts @ldt, 0 |
| 50 | + |
| 51 | + source "/tmp/countmin.b" |
| 52 | + |
| 53 | +The location of the source file when it was compiled by the limbo compiler will |
| 54 | +influence the value presented in the output of the list() method. |
| 55 | + |
| 56 | +Tests |
| 57 | +----- |
| 58 | + |
| 59 | +Some tests that write .dis files are included in the Tests directory. These |
| 60 | +will try to create the corresponding .dis files to their equivalent Limbo |
| 61 | +programs. Ensure that the package directory is on the PYTHONPATH and run them |
| 62 | +in the following way: |
| 63 | + |
| 64 | + PYTHONPATH=. ./Tests/countmin.py /tmp/countmin.dis |
| 65 | + |
| 66 | +You should then be able to run them in the Inferno emulator and inspect them |
| 67 | +using the method described in the previous section. |
| 68 | + |
| 69 | +Authors and License |
| 70 | +------------------- |
| 71 | + |
| 72 | +David Boddie <david@boddie.org.uk> |
| 73 | + |
| 74 | +Unless indicated otherwise, the contents of this package are licensed under the |
| 75 | +GNU General Public License version 3 (or later). |
| 76 | + |
| 77 | + Copyright (C) 2017 David Boddie <david@boddie.org.uk> |
| 78 | + |
| 79 | + This program is free software: you can redistribute it and/or modify |
| 80 | + it under the terms of the GNU General Public License as published by |
| 81 | + the Free Software Foundation, either version 3 of the License, or |
| 82 | + (at your option) any later version. |
| 83 | + |
| 84 | + This program is distributed in the hope that it will be useful, |
| 85 | + but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 86 | + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 87 | + GNU General Public License for more details. |
| 88 | + |
| 89 | + You should have received a copy of the GNU General Public License |
| 90 | + along with this program. If not, see <http://www.gnu.org/licenses/>. |
| 91 | + |
| 92 | +References |
| 93 | +---------- |
| 94 | + |
| 95 | +[1] http://inferno-os.org/inferno/papers/dis.html |
| 96 | +[2] http://inferno-os.org |
| 97 | +[3] http://inferno-os.org/inferno/papers/limbo.html |