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Fix reading partial objects #27

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Fix reading partial objects #27

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Commits on Feb 15, 2021

  1. Fix crash in DcmFileFormat::readUntilTag() when reading a partial met… 

    …a info

Use case:
* DcmFileFormat::readUntilTag() (called from DcmFileFormat::read())
  tries to read DcmMetaInfo which is partially available in input
  stream
* DcmMetaInfo::read() returns EC_StreamNotifyClient
* DcmFileFormat::readUntilTag() does not check the returned condition
  and tries to use DcmMetaInfo (by calling lookForXfer()) even though
  the object is not completely read. By using it, DcmFileFormat
  changes meta info's current elemetnt to have index -1.
* next time DcmFileFormat::readUntilTag() is called, it tries to finish
  reading last incomplete object. Having its current index set to -1
  that leads to a crash

Fix:
* check returned condition from DcmMetaInfo::read() and exit early
  if it is bad
    @akaraivanov
    akaraivanov committed Feb 15, 2021
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  2. Fix bug in DcmMetaInfo::read() when reading incomplete in stream object 

    Use case:
* DcmMetaInfo::read() is called to read object which is partially
  available in input stream
* Transfer syntax is detected from the preamble and is stored in
  member variable Xfer
* On the second call to DcmMetaInfo::read() the stored transfer syntax is
  overwritten with the value of the input transfer syntax (typically EXS_Unknown).
  This time preamble is already read and is not used to detect transfer syntax.
  If input parameter is equal to EXS_Unknown current transfer syntax
  is maintained in local vairable newxfer will also be EXS_Unknown.
  Calling readGroupLength() with EXS_Unknown will return condition
  EC_IllegalCall and that is the be also the returned value of
  DcmMetaInfo::read()

Fix:
* do not overwrite store transfer syntax in Xfer if object's transfer has started
* use stored transfer syntax on consecutive calls
    @akaraivanov
    akaraivanov committed Feb 15, 2021
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    80a0851 View commit details
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