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      1 =====================================
      2 The Module Information Stream
      3 =====================================
      4 
      5 .. contents::
      6    :local:
      7 
      8 .. _modi_stream_intro:
      9 
     10 Introduction
     11 ============
     12 
     13 The Module Info Stream (henceforth referred to as the Modi stream) contains
     14 information about a single module (object file, import library, etc that
     15 contributes to the binary this PDB contains debug information about.  There
     16 is one modi stream for each module, and the mapping between modi stream index
     17 and module is contained in the :doc:`DBI Stream <DbiStream>`.  The modi stream
     18 for a single module contains line information for the compiland, as well as
     19 all CodeView information for the symbols defined in the compiland.  Finally,
     20 there is a "global refs" substream which is not well understood.
     21 
     22 .. _modi_stream_layout:
     23 
     24 Stream Layout
     25 =============
     26 
     27 A modi stream is laid out as follows:
     28 
     29 
     30 .. code-block:: c++
     31 
     32   struct ModiStream {
     33     uint32_t Signature;
     34     uint8_t Symbols[SymbolSize-4];
     35     uint8_t C11LineInfo[C11Size];
     36     uint8_t C13LineInfo[C13Size];
     37     
     38     uint32_t GlobalRefsSize;
     39     uint8_t GlobalRefs[GlobalRefsSize];
     40   };
     41 
     42 - **Signature** - Unknown.  In practice only the value of ``4`` has been
     43   observed.  It is hypothesized that this value corresponds to the set of
     44   ``CV_SIGNATURE_xx`` defines in ``cvinfo.h``, with the value of ``4``
     45   meaning that this module has C13 line information (as opposed to C11 line
     46   information).  A corollary of this is that we expect to only ever see
     47   C13 line info, and that we do not understand the format of C11 line info.
     48   
     49 - **Symbols** - The :ref:`CodeView Symbol Substream <modi_symbol_substream>`.
     50   ``SymbolSize`` is equal to the value of ``SymByteSize`` for the
     51   corresponding module's entry in the :ref:`Module Info Substream <dbi_mod_info_substream>`
     52   of the :doc:`DBI Stream <DbiStream>`.
     53 
     54 - **C11LineInfo** - A block containing CodeView line information in C11
     55   format.  ``C11Size`` is equal to the value of ``C11ByteSize`` from the
     56   :ref:`Module Info Substream <dbi_mod_info_substream>` of the
     57   :doc:`DBI Stream <DbiStream>`.  If this value is ``0``, then C11 line
     58   information is not present.  As mentioned previously, the format of
     59   C11 line info is not understood and we assume all line in modern PDBs
     60   to be in C13 format.
     61   
     62 - **C13LineInfo** - A block containing CodeView line information in C13
     63   format.  ``C13Size`` is equal to the value of ``C13ByteSize`` from the
     64   :ref:`Module Info Substream <dbi_mod_info_substream>` of the
     65   :doc:`DBI Stream <DbiStream>`.  If this value is ``0``, then C13 line
     66   information is not present.
     67   
     68 - **GlobalRefs** - The meaning of this substream is not understood.
     69 
     70 .. _modi_symbol_substream:
     71 
     72 The CodeView Symbol Substream
     73 =============================
     74 
     75 The CodeView Symbol Substream.  This is an array of variable length
     76 records describing the functions, variables, inlining information,
     77 and other symbols defined in the compiland.  The entire array consumes
     78 ``SymbolSize-4`` bytes.  The format of a CodeView Symbol Record (and
     79 thusly, an array of CodeView Symbol Records) is described in
     80 :doc:`CodeViewSymbols`.
     81