<p>laforge <strong>submitted</strong> this change.</p><p><a href="https://gerrit.osmocom.org/c/pysim/+/24450">View Change</a></p><div style="white-space:pre-wrap">Approvals:
Jenkins Builder: Verified
laforge: Looks good to me, approved
</div><pre style="font-family: monospace,monospace; white-space: pre-wrap;">utils: Add bertlv_encode_tag()<br><br>We so far had decoders for BER-TLV tags, but no encoder yet.<br><br>Change-Id: I4183546bed9d6232ddcefad764f4e67afcf8b2ed<br>---<br>M pySim/utils.py<br>1 file changed, 45 insertions(+), 0 deletions(-)<br><br></pre><pre style="font-family: monospace,monospace; white-space: pre-wrap;"><span>diff --git a/pySim/utils.py b/pySim/utils.py</span><br><span>index 74655d4..777638c 100644</span><br><span>--- a/pySim/utils.py</span><br><span>+++ b/pySim/utils.py</span><br><span>@@ -212,6 +212,51 @@</span><br><span> i += 1</span><br><span> return ({'class':cls, 'constructed':constructed, 'tag':tag}, binary[i:])</span><br><span> </span><br><span style="color: hsl(120, 100%, 40%);">+def bertlv_encode_tag(t) -> bytes:</span><br><span style="color: hsl(120, 100%, 40%);">+ """Encode a single Tag value according to ITU-T X.690 8.1.2</span><br><span style="color: hsl(120, 100%, 40%);">+ """</span><br><span style="color: hsl(120, 100%, 40%);">+ def get_top7_bits(inp:int) -> Tuple[int, int]:</span><br><span style="color: hsl(120, 100%, 40%);">+ """Get top 7 bits of integer. Returns those 7 bits as integer and the remaining LSBs."""</span><br><span style="color: hsl(120, 100%, 40%);">+ remain_bits = inp.bit_length()</span><br><span style="color: hsl(120, 100%, 40%);">+ if remain_bits >= 7:</span><br><span style="color: hsl(120, 100%, 40%);">+ bitcnt = 7</span><br><span style="color: hsl(120, 100%, 40%);">+ else:</span><br><span style="color: hsl(120, 100%, 40%);">+ bitcnt = remain_bits</span><br><span style="color: hsl(120, 100%, 40%);">+ outp = inp >> (remain_bits - bitcnt)</span><br><span style="color: hsl(120, 100%, 40%);">+ remainder = inp & ~ (inp << (remain_bits - bitcnt))</span><br><span style="color: hsl(120, 100%, 40%);">+ return outp, remainder</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+ if isinstance(t, int):</span><br><span style="color: hsl(120, 100%, 40%);">+ # FIXME: multiple byte tags</span><br><span style="color: hsl(120, 100%, 40%);">+ tag = t & 0x1f</span><br><span style="color: hsl(120, 100%, 40%);">+ constructed = True if t & 0x20 else False</span><br><span style="color: hsl(120, 100%, 40%);">+ cls = t >> 6</span><br><span style="color: hsl(120, 100%, 40%);">+ else:</span><br><span style="color: hsl(120, 100%, 40%);">+ tag = t['tag']</span><br><span style="color: hsl(120, 100%, 40%);">+ constructed = t['constructed']</span><br><span style="color: hsl(120, 100%, 40%);">+ cls = t['class']</span><br><span style="color: hsl(120, 100%, 40%);">+ if tag <= 30:</span><br><span style="color: hsl(120, 100%, 40%);">+ t = tag & 0x1f</span><br><span style="color: hsl(120, 100%, 40%);">+ if constructed:</span><br><span style="color: hsl(120, 100%, 40%);">+ t |= 0x20</span><br><span style="color: hsl(120, 100%, 40%);">+ t |= (cls & 3) << 6</span><br><span style="color: hsl(120, 100%, 40%);">+ return bytes([t])</span><br><span style="color: hsl(120, 100%, 40%);">+ else: # multi-byte tag</span><br><span style="color: hsl(120, 100%, 40%);">+ t = 0x1f;</span><br><span style="color: hsl(120, 100%, 40%);">+ if constructed:</span><br><span style="color: hsl(120, 100%, 40%);">+ t |= 0x20</span><br><span style="color: hsl(120, 100%, 40%);">+ t |= (cls & 3) << 6</span><br><span style="color: hsl(120, 100%, 40%);">+ tag_bytes = bytes([t])</span><br><span style="color: hsl(120, 100%, 40%);">+ remain = tag</span><br><span style="color: hsl(120, 100%, 40%);">+ while True:</span><br><span style="color: hsl(120, 100%, 40%);">+ t, remain = get_top7_bits(remain)</span><br><span style="color: hsl(120, 100%, 40%);">+ if remain:</span><br><span style="color: hsl(120, 100%, 40%);">+ t |= 0x80</span><br><span style="color: hsl(120, 100%, 40%);">+ tag_bytes += bytes([t])</span><br><span style="color: hsl(120, 100%, 40%);">+ if not remain:</span><br><span style="color: hsl(120, 100%, 40%);">+ break</span><br><span style="color: hsl(120, 100%, 40%);">+ return tag_bytes</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span> def bertlv_parse_len(binary:bytes) -> Tuple[int, bytes]:</span><br><span> """Parse a single Length value according to ITU-T X.690 8.1.3;</span><br><span> only the definite form is supported here.</span><br><span></span><br></pre><p>To view, visit <a href="https://gerrit.osmocom.org/c/pysim/+/24450">change 24450</a>. To unsubscribe, or for help writing mail filters, visit <a href="https://gerrit.osmocom.org/settings">settings</a>.</p><div itemscope itemtype="http://schema.org/EmailMessage"><div itemscope itemprop="action" itemtype="http://schema.org/ViewAction"><link itemprop="url" href="https://gerrit.osmocom.org/c/pysim/+/24450"/><meta itemprop="name" content="View Change"/></div></div>
<div style="display:none"> Gerrit-Project: pysim </div>
<div style="display:none"> Gerrit-Branch: master </div>
<div style="display:none"> Gerrit-Change-Id: I4183546bed9d6232ddcefad764f4e67afcf8b2ed </div>
<div style="display:none"> Gerrit-Change-Number: 24450 </div>
<div style="display:none"> Gerrit-PatchSet: 2 </div>
<div style="display:none"> Gerrit-Owner: laforge <laforge@osmocom.org> </div>
<div style="display:none"> Gerrit-Reviewer: Jenkins Builder </div>
<div style="display:none"> Gerrit-Reviewer: dexter <pmaier@sysmocom.de> </div>
<div style="display:none"> Gerrit-Reviewer: fixeria <vyanitskiy@sysmocom.de> </div>
<div style="display:none"> Gerrit-Reviewer: laforge <laforge@osmocom.org> </div>
<div style="display:none"> Gerrit-Reviewer: pespin <pespin@sysmocom.de> </div>
<div style="display:none"> Gerrit-MessageType: merged </div>