balst_resolver_dwarfreader.h

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/// @file balst_resolver_dwarfreader.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// balst_resolver_dwarfreader.h                                       -*-C++-*-
 
#ifndef INCLUDED_BALST_RESOLVER_DWARFREADER
#define INCLUDED_BALST_RESOLVER_DWARFREADER
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup balst_resolver_dwarfreader balst_resolver_dwarfreader
/// @brief  Provide mechanism for reading DWARF information from object files.
/// @addtogroup bal
/// @{
/// @addtogroup balst
/// @{
/// @addtogroup balst_resolver_dwarfreader
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#balst_resolver_dwarfreader-purpose"> Purpose</a>
/// * <a href="#balst_resolver_dwarfreader-classes"> Classes </a>
/// * <a href="#balst_resolver_dwarfreader-description"> Description </a>
///   * <a href="#balst_resolver_dwarfreader-usage"> Usage </a>
///
/// # Purpose {#balst_resolver_dwarfreader-purpose}
/// Provide mechanism for reading DWARF information from object files.
///
/// # Classes {#balst_resolver_dwarfreader-classes}
///
/// -   balst::Resolver_DwarfReader: reading mechanism
///
/// @see  balst_resolverimpl_elf
///           balst_resolver_filehelper
///
/// # Description {#balst_resolver_dwarfreader-description}
/// This component provides a class,
/// `balst::Resolver_DwarfReader`, that is optimized for reading
/// information from object files that are in the DWARF format.  The Elf object
/// file format is used on Linux and Solaris platforms, and the DWARF file
/// format is used within ELF files to encode source file name and line number
/// information.  The Elf format is described by documents at:
/// * `http://en.wikipedia.org/wiki/Executable_and_Linkable_Format`
/// * `http://downloads.openwatcom.org/ftp/devel/docs/elf-64-gen.pdf`
/// * `http://www.sco.com/developers/gabi/latest/contents.html`
/// The DWARF format is described by documents at:
/// * `http://dwarfstd.org`
///
/// Note that this file does not include everything necessary to resolve DWARF
/// information.  Most of that functionality is in
/// @ref balst_resolverimpl_elf , and this component only describe a tool
/// used within that effort.
///
/// ## Usage {#balst_resolver_dwarfreader-usage}
///
///
/// This component is an implementation detail of `balst` and is *not* intended
/// for direct client use.  It is subject to change without notice.  As such, a
/// usage example is not provided.
/// @}
/** @} */
/** @} */
 
/** @addtogroup bal
 * @{
 */
/** @addtogroup balst
 * @{
 */
/** @addtogroup balst_resolver_dwarfreader
 * @{
 */
 
#include <balscm_version.h>
 
#include <balst_objectfileformat.h>
#include <balst_resolver_filehelper.h>
 
#include <bdlb_bitutil.h>
 
#include <bdls_filesystemutil.h>
 
#include <bslmf_assert.h>
 
#include <bsls_assert.h>
#include <bsls_platform.h>
#include <bsls_review.h>
#include <bsls_types.h>
 
#include <bsl_cstddef.h>
#include <bsl_cstring.h>
#include <bsl_string.h>
 
 
namespace balst {
 
#if defined(BALST_OBJECTFILEFORMAT_RESOLVER_DWARF)
 
                            // ==========================
                            // class Resolver_DwarfReader
                            // ==========================
 
class Resolver_DwarfReader {
  public:
    // PUBLIC TYPES
    typedef bdls::FilesystemUtil::Offset Offset;
    typedef bsls::Types::UintPtr         UintPtr;
    typedef bsls::Types::IntPtr          IntPtr;
    typedef bsls::Types::Uint64          Uint64;
 
    struct Section {
        // Refers to one section of a segment.
 
        // DATA
        Offset d_offset;    // offset of the section in the file
        Offset d_size;      // size of that section in bytes
 
        // CREATOR
        Section();
            // Create a zero-value 'Section' object.
 
        // MANIPULATOR
        void reset(Offset offset = 0, Offset size = 0);
            // Reset this 'Section' object to have the specified 'offset' and
            // the specified 'size'.
    };
 
    // PUBLIC CONSTANTS
    enum { k_SCRATCH_BUF_LEN =
                              Resolver_FileHelper::k_DEFAULT_SCRATCH_BUF_LEN };
 
                               // DWARF enums
 
    // The DWARF documents are at: http://www.dwarfstd.org/Download.php.
    //
    // The DWARF specs specify no 'struct's, only several hundred identifiers
    // of the form 'DW_*' defining integer values.  Some sources provide
    // include files 'dwarf.h' specifying 'enum's for all these values, but
    // accessing these include files from DPKG proved problematic, and the
    // versions available only provided DWARF 3 identifiers and we needed some
    // DWARF 4 id's too.  The 'dwarf.h' available from Red Hat was LGPL'ed,
    // posing potential licensing problems with copying or cut/pasting it into
    // the BDE code base, which is licensed more permissively than LGPL.
    //
    // The simplest approach was to implement these enums directly copying them
    // from the spec.  The following are a subset of all the id's in the spec,
    // limited to the ones we use in this package.
    //
    // Rather than name the enum's 'DW_*' as they appear in the spec, we name
    // them 'e_DW_*' according to BDE convention.
 
    enum Dwarf3Enums {
        // These values were obtained from the DWARF 3 Spec.
 
        e_DW_AT_sibling = 0x01,
        e_DW_AT_location = 0x02,
        e_DW_AT_name = 0x03,
        e_DW_AT_ordering = 0x09,
        e_DW_AT_byte_size = 0x0b,
        e_DW_AT_bit_offset = 0x0c,
        e_DW_AT_bit_size = 0x0d,
        e_DW_AT_stmt_list = 0x10,
        e_DW_AT_low_pc = 0x11,
        e_DW_AT_high_pc = 0x12,
        e_DW_AT_language = 0x13,
        e_DW_AT_discr = 0x15,
        e_DW_AT_discr_value = 0x16,
        e_DW_AT_visibility = 0x17,
        e_DW_AT_import = 0x18,
        e_DW_AT_string_length = 0x19,
        e_DW_AT_common_reference = 0x1a,
        e_DW_AT_comp_dir = 0x1b,
        e_DW_AT_const_value = 0x1c,
        e_DW_AT_containing_type = 0x1d,
        e_DW_AT_default_value = 0x1e,
        e_DW_AT_inline = 0x20,
        e_DW_AT_is_optional = 0x21,
        e_DW_AT_lower_bound = 0x22,
        e_DW_AT_producer = 0x25,
        e_DW_AT_prototyped = 0x27,
        e_DW_AT_return_addr = 0x2a,
        e_DW_AT_start_scope = 0x2c,
        e_DW_AT_bit_stride = 0x2e,
        e_DW_AT_upper_bound = 0x2f,
        e_DW_AT_abstract_origin = 0x31,
        e_DW_AT_accessibility = 0x32,
        e_DW_AT_address_class = 0x33,
        e_DW_AT_artificial = 0x34,
        e_DW_AT_base_types = 0x35,
        e_DW_AT_calling_convention = 0x36,
        e_DW_AT_count = 0x37,
        e_DW_AT_data_member_location = 0x38,
        e_DW_AT_decl_column = 0x39,
        e_DW_AT_decl_file = 0x3a,
        e_DW_AT_decl_line = 0x3b,
        e_DW_AT_declaration = 0x3c,
        e_DW_AT_discr_list = 0x3d,
        e_DW_AT_encoding = 0x3e,
        e_DW_AT_external = 0x3f,
        e_DW_AT_frame_base = 0x40,
        e_DW_AT_friend = 0x41,
        e_DW_AT_identifier_case = 0x42,
        e_DW_AT_macro_info = 0x43,
        e_DW_AT_namelist_item = 0x44,
        e_DW_AT_priority = 0x45,
        e_DW_AT_segment = 0x46,
        e_DW_AT_specification = 0x47,
        e_DW_AT_static_link = 0x48,
        e_DW_AT_type = 0x49,
        e_DW_AT_use_location = 0x4a,
        e_DW_AT_variable_parameter = 0x4b,
        e_DW_AT_virtuality = 0x4c,
        e_DW_AT_vtable_elem_location = 0x4d,
        e_DW_AT_allocated = 0x4e,
        e_DW_AT_associated = 0x4f,
        e_DW_AT_data_location = 0x50,
        e_DW_AT_byte_stride = 0x51,
        e_DW_AT_entry_pc = 0x52,
        e_DW_AT_use_UTF8 = 0x53,
        e_DW_AT_extension = 0x54,
        e_DW_AT_ranges = 0x55,
        e_DW_AT_trampoline = 0x56,
        e_DW_AT_call_column = 0x57,
        e_DW_AT_call_file = 0x58,
        e_DW_AT_call_line = 0x59,
        e_DW_AT_description = 0x5a,
        e_DW_AT_binary_scale = 0x5b,
        e_DW_AT_decimal_scale = 0x5c,
        e_DW_AT_small = 0x5d,
        e_DW_AT_decimal_sign = 0x5e,
        e_DW_AT_digit_count = 0x5f,
        e_DW_AT_picture_string = 0x60,
        e_DW_AT_mutable = 0x61,
        e_DW_AT_threads_scaled = 0x62,
        e_DW_AT_explicit = 0x63,
        e_DW_AT_object_pointer = 0x64,
        e_DW_AT_endianity = 0x65,
        e_DW_AT_elemental = 0x66,
        e_DW_AT_pure = 0x67,
        e_DW_AT_recursive = 0x68,
 
        e_DW_CHILDREN_no = 0x00,
        e_DW_CHILDREN_yes = 0x01,
 
        e_DW_FORM_addr = 0x01,
        e_DW_FORM_block2 = 0x03,
        e_DW_FORM_block4 = 0x04,
        e_DW_FORM_data2 = 0x05,
        e_DW_FORM_data4 = 0x06,
        e_DW_FORM_data8 = 0x07,
        e_DW_FORM_string = 0x08,
        e_DW_FORM_block = 0x09,
        e_DW_FORM_block1 = 0x0a,
        e_DW_FORM_data1 = 0x0b,
        e_DW_FORM_flag = 0x0c,
        e_DW_FORM_sdata = 0x0d,
        e_DW_FORM_strp = 0x0e,
        e_DW_FORM_udata = 0x0f,
        e_DW_FORM_ref_addr = 0x10,
        e_DW_FORM_ref1 = 0x11,
        e_DW_FORM_ref2 = 0x12,
        e_DW_FORM_ref4 = 0x13,
        e_DW_FORM_ref8 = 0x14,
        e_DW_FORM_ref_udata = 0x15,
        e_DW_FORM_indirect = 0x16,
        e_DW_FORM_line_strp = 0x1f,
 
        e_DW_INL_declared_inlined = 0x03,
 
        e_DW_LNCT_path = 0x01,
        e_DW_LNCT_directory_index = 0x02,
        e_DW_LNCT_timestamp = 0x03,
        e_DW_LNCT_size = 0x04,
        e_DW_LNCT_MD5 = 0x05,
        e_DW_LNCT_lo_user = 0x2000,
        e_DW_LNCT_hi_user = 0x3fff,
 
        e_DW_LNE_end_sequence = 0x01,
        e_DW_LNE_set_address = 0x02,
        e_DW_LNE_define_file = 0x03,
 
        e_DW_LNS_copy = 0x01,
        e_DW_LNS_advance_pc = 0x02,
        e_DW_LNS_advance_line = 0x03,
        e_DW_LNS_set_file = 0x04,
        e_DW_LNS_set_column = 0x05,
        e_DW_LNS_negate_stmt = 0x06,
        e_DW_LNS_set_basic_block = 0x07,
        e_DW_LNS_const_add_pc = 0x08,
        e_DW_LNS_fixed_advance_pc = 0x09,
        e_DW_LNS_set_prologue_end = 0x0a,
        e_DW_LNS_set_epilogue_begin = 0x0b,
        e_DW_LNS_set_isa = 0x0c,
 
        e_DW_TAG_array_type = 0x01,
        e_DW_TAG_class_type = 0x02,
        e_DW_TAG_entry_point = 0x03,
        e_DW_TAG_enumeration_type = 0x04,
        e_DW_TAG_formal_parameter = 0x05,
        e_DW_TAG_imported_declaration = 0x08,
        e_DW_TAG_label = 0x0a,
        e_DW_TAG_lexical_block = 0x0b,
        e_DW_TAG_member = 0x0d,
        e_DW_TAG_pointer_type = 0x0f,
        e_DW_TAG_reference_type = 0x10,
        e_DW_TAG_compile_unit = 0x11,
        e_DW_TAG_string_type = 0x12,
        e_DW_TAG_structure_type = 0x13,
        e_DW_TAG_subroutine_type = 0x15,
        e_DW_TAG_typedef = 0x16,
        e_DW_TAG_union_type = 0x17,
        e_DW_TAG_unspecified_parameters = 0x18,
        e_DW_TAG_variant = 0x19,
        e_DW_TAG_common_block = 0x1a,
        e_DW_TAG_common_inclusion = 0x1b,
        e_DW_TAG_inheritance = 0x1c,
        e_DW_TAG_inlined_subroutine = 0x1d,
        e_DW_TAG_module = 0x1e,
        e_DW_TAG_ptr_to_member_type = 0x1f,
        e_DW_TAG_set_type = 0x20,
        e_DW_TAG_subrange_type = 0x21,
        e_DW_TAG_with_stmt = 0x22,
        e_DW_TAG_access_declaration = 0x23,
        e_DW_TAG_base_type = 0x24,
        e_DW_TAG_catch_block = 0x25,
        e_DW_TAG_const_type = 0x26,
        e_DW_TAG_constant = 0x27,
        e_DW_TAG_enumerator = 0x28,
        e_DW_TAG_file_type = 0x29,
        e_DW_TAG_friend = 0x2a,
        e_DW_TAG_namelist = 0x2b,
        e_DW_TAG_namelist_item = 0x2c,
        e_DW_TAG_packed_type = 0x2d,
        e_DW_TAG_subprogram = 0x2e,
        e_DW_TAG_template_type_parameter = 0x2f,
        e_DW_TAG_template_value_parameter = 0x30,
        e_DW_TAG_thrown_type = 0x31,
        e_DW_TAG_try_block = 0x32,
        e_DW_TAG_variant_part = 0x33,
        e_DW_TAG_variable = 0x34,
        e_DW_TAG_volatile_type = 0x35,
        e_DW_TAG_dwarf_procedure = 0x36,
        e_DW_TAG_restrict_type = 0x37,
        e_DW_TAG_interface_type = 0x38,
        e_DW_TAG_namespace = 0x39,
        e_DW_TAG_imported_module = 0x3a,
        e_DW_TAG_unspecified_type = 0x3b,
        e_DW_TAG_partial_unit = 0x3c,
        e_DW_TAG_imported_unit = 0x3d,
        e_DW_TAG_condition = 0x3f,
        e_DW_TAG_shared_type = 0x40,
        e_DW_TAG_lo_user = 0x4080,
        e_DW_TAG_hi_user = 0xffff
    };
 
    enum Dwarf4Enums {
        // These values were obtained from the DWARF 4 Spec.
 
        e_DW_AT_signature = 0x69,
        e_DW_AT_main_subprogram = 0x6a,
        e_DW_AT_data_bit_offset = 0x6b,
        e_DW_AT_const_expr = 0x6c,
        e_DW_AT_enum_class = 0x6d,
        e_DW_AT_linkage_name = 0x6e,
        e_DW_AT_lo_user = 0x2000,
        e_DW_AT_hi_user = 0x3fff,
 
        e_DW_FORM_sec_offset = 0x17,
        e_DW_FORM_exprloc = 0x18,
        e_DW_FORM_flag_present = 0x19,
        e_DW_FORM_ref_sig8 = 0x20,
 
        e_DW_LNE_set_discriminator = 0x04,
 
        e_DW_TAG_mutable_type = 0x3e,
        e_DW_TAG_type_unit = 0x41,
        e_DW_TAG_rvalue_reference_type = 0x42,
        e_DW_TAG_template_alias = 0x43
    };
 
    enum Dwarf5Enums {
        e_DW_UT_compile = 0x1,
        e_DW_UT_type = 0x2,
        e_DW_UT_partial = 0x3,
        e_DW_UT_skeleton = 0x4,
        e_DW_UT_split_compile = 0x5,
        e_DW_UT_split_type = 0x6,
        e_DW_UT_lo_user = 0x80,
        e_DW_UT_hi_user = 0xff
    };
 
  private:
    // DATA
    balst::Resolver_FileHelper     *d_helper_p;      // filehelper for current
                                                     // segment
 
    char                           *d_buffer_p;      // buffer.
                                                     // k_SCRATCH_BUF_LEN long
 
    Offset                          d_offset;        // offset last read from
 
    Offset                          d_beginOffset;   // beg of current section
 
    Offset                          d_endOffset;     // end of current section
 
    const char                     *d_readPtr;       // current place to read
                                                     // from (in the buffer)
 
    const char                     *d_endPtr;        // end of what's in buffer
 
    int                             d_offsetSize;    // offset size determined
                                                     // by 'readInitalLength'
 
    int                             d_addressSize;   // address read by
                                                     // 'getAddress' or set by
                                                     // 'setAddressSize'.
 
  private:
    // NOT IMPLEMENTED
    Resolver_DwarfReader(const Resolver_DwarfReader&);
    Resolver_DwarfReader& operator=(const Resolver_DwarfReader&);
 
  private:
    // PRIVATE MANIPULATORS
 
    /// Determine if we are able to read the specified `numBytes` from
    /// `d_buffer`.  If not, `reload` is used to attempt to accomodate this
    /// `needBytes` request.  Return 0 if we are able to read `numBytes`
    /// from `d_buffer` after this invocation of `needBytes`, and a non-zero
    /// value otherwise.
    int needBytes(bsl::size_t numBytes);
 
    /// Reload the buffer to accomodate a read of at least the specified
    /// `numBytes`.  If possible, read up to the end of the section or the
    /// size of the buffer, whichever is shorter.  Return 0 on success, and
    /// a non-zero value otherwise.
    int reload(bsl::size_t numBytes);
 
  public:
    // CLASS METHODS
    static
    const char *stringForAt(unsigned id);
        // Return the string equivalent of the specified 'e_DW_AT_*' 'id'.
 
    static
    const char *stringForForm(unsigned id);
        // Return the string equivalent of the specified 'e_DW_FORM_*' 'id'.
 
    static
    const char *stringForInlineState(unsigned inlineState);
        // Return the string equivalent of the specified 'e_DW_INL_*'
        // 'inlineState'.
 
    static
    const char *stringForLNCT(unsigned id);
        // Return the string equivalent of the specified 'e_DW_LNCT_*' 'id'.
 
    static
    const char *stringForLNE(unsigned id);
        // Return the string equivalent of the specified 'e_DW_LNE_*' 'id'.
 
    static
    const char *stringForLNS(unsigned id);
        // Return the string equivalent of the specified 'e_DW_LNS_*' 'id'.
 
    static
    const char *stringForTag(unsigned tag);
        // Return the string equivalent of the specified 'e_DW_TAG_*' 'tag'.
 
    // CREATORS
 
    /// Create a `Reader` object in a null state.
    Resolver_DwarfReader();
 
    /// Destroy this object.
     ~Resolver_DwarfReader() = default;
 
    // MANIPULATORS
 
    /// Disable this object for further use.
    void disable();
 
    /// Initialize this `Reader` object using the specified `fileHelper` and
    /// the specified `buffer`, to operate on the specified `section`, where
    /// the specified `libraryFileSize` is the size of the library or
    /// executable file.  `buffer` is assumed to be at least
    /// `k_SCRATCH_BUF_LEN` long.
    int init(balst::Resolver_FileHelper *fileHelper,
             char                       *buffer,
             const Section&              section,
             Offset                      libraryFileSize);
 
    /// Read to the specified `dst`.  This function will fail if
    /// `d_addressSize` has not been initialized by `readAddressSize` or
    /// `setAddressSize`.  Return 0 on success and a non-zero value
    /// otherwise.
    int readAddress(UintPtr *dst);
 
    /// Read to the specified `dst` according to the specified `form`.
    /// Return 0 on success and a non-zero value otherwise.
    int readAddress(UintPtr *dst, unsigned form);
 
    /// Read the address size from a single unsigned byte, check it, and
    /// assign `d_addressSize` to it.  Return 0 on success and a non-zero
    /// value otherwise.  It is an error if address size is not equal to the
    /// size of an `unsigned int` or of a `void *`.
    int readAddressSize();
 
    /// Read the initial length of the object according to the DWARF
    /// specification to the specified `*dst`, which is an 8-byte value.
    /// Read `*dst` first as a 4 byte value, setting the high-order 4 bytes
    /// to 0, and if the value is below 0xfffffff0, then that indicates that
    /// section offsets are to be read as 4 byte values within the object
    /// whose length is specified.  If the value is 0xffffffff, read the
    /// next 8 bytes into `*dst` and that indicates that section offsets are
    /// to be 8 bytes within the object whose length is specified.
    /// Initialize `d_offsetSize` accordingly.  Values in the range
    /// `[0xfffffff0, 0xffffffff)` are illegal for that first 4 bytes. Return 0 on success and a non-zero value otherwise.  
    /// 
    /// \note Note that   when
    /// we read a 4-byte value, we do not extend sign to the high order 4
    /// bytes of `*dst`.
    int readInitialLength(Offset *dst);
 
    /// Read a signed, variable-length number into the specified `*dst`.
    /// Return 0 on success and a non-zero value otherwise.
    template <class TYPE>
    int readLEB128(TYPE *dst);
 
    /// Read an unsigned, variable-length number into the specified `*dst`.
    /// Return 0 on success and a non-zero value otherwise.
    template <class TYPE>
    int readULEB128(TYPE *dst);
 
    /// Read to the specified `*dst`, where the specified `offsetSize` is the
    /// number of low-order bytes to be read into the offset, where `*dst` is 8
    /// bytes, and extra high-order bytes are to be set to 0.  Do not extend
    /// sign.  Return 0 on success and a non-zero value otherwise.
    int readOffset(Offset      *dst,
                   bsl::size_t  offsetSize);
 
    /// Read to the specified `*dst` according to the specified `form`, where
    /// `form` is a DWARF enum of the `e_DW_FORM_*` category.  Return 0 on
    /// success and a non-zero value otherwise.
    int readOffsetFromForm(Offset   *dst,
                           unsigned  form);
 
    /// Read to the specified offset `*dst` according to `d_offsetSize`. Return 0 on success and a non-zero value otherwise.  
    /// 
    /// \note Note that   when
    /// the offset read is only 4 bytes, no sign extension takes place as
    /// we always expect a positive result.
    int readSectionOffset(Offset *dst);
 
    /// Read a null-terminated string to the specified `*dst`.  If no `dst`
    /// is specified, skip over the string without copying it.  This
    /// function will fail if the string length is greater than
    /// `k_SCRATCH_BUFFER_LEN - 1`.
    int readString(bsl::string *dst = 0);
 
    /// Read a null terminated string to the specified `*dst` from the specified `offset` plus `d_beginOffset`.  
    /// 
    /// \note Note that,   unlike most of
    /// the other `read` functions, this one is intended for random access
    /// so does not read a full buffer ahead, instead reading a fairly
    /// minimal amount of data near the specified location.
    int readStringAt(bsl::string *dst, Offset offset);
 
    /// Read to the specified string either from the current reader (if the
    /// specified `form` is `e_DW_FORM_string`) or read an offset from the
    /// current reader, then use that to read the string either from the
    /// specified `*strReader` (if `form` is `e_DW_FORM_strp`) or from the
    /// specified `*lineStrReader` (if `form` is `e_DW_FORM_line_strp`).
    /// Return 0 on success and a non-zero value otherwise.
    int readStringFromForm(bsl::string          *dst,
                           Resolver_DwarfReader *strReader,
                           Resolver_DwarfReader *lineStrReader,
                           unsigned              form);
 
    /// Read a value into the specified `*dst`, assuming that it is represented
    /// by `sizeof(*dst)` bytes.
    template <class TYPE>
    int readValue(TYPE *dst);
 
    /// Explicitly set the `d_addressSize` of this reader to the specified
    /// `size`.  This function will fail unless the size is the
    /// `sizeof(unsigned) == size` or `sizeof(UintPtr) == size`.
    int setAddressSize(unsigned size);
 
    /// Set the end offset to the specified `newOffset`.
    int setEndOffset(Offset newOffset);
 
    /// Skip forward over the specified `bytes` without reading them.
    int skipBytes(Offset bytes);
 
    /// Skip over a null terminated string without copying it.
    int skipString();
 
    /// Skip over data according to the specified `form`, which is an enum
    /// of type `e_DW_FORM_*`.
    int skipForm(unsigned form);
 
    /// Skip to the specified `offset`, which must be in the section associated
    /// with this reader.  Return 0 on success and a non-zero value otherwise.
    int skipTo(Offset offset);
 
    /// Skip a variable-length integer.  Note this will work for both
    /// LEB128's and ULEB128's.
    int skipULEB128();
 
    // ACCESSORS
 
    /// Return the address size field.
    int addressSize() const;
 
    /// Return `true` if the reader has reached the end of the section and
    /// `false` otherwise.
    bool atEndOfSection() const;
 
    /// Return the current offset taking the `d_reader` position into account.
    Offset offset() const;
 
    /// Return the offset length that was set by the `readInitialLength`
    /// function.
    Offset offsetSize() const;
 
    /// Return `false` if this reader is disabled and `true` otherwise.
    bool isEnabled() const;
};
 
// PRIVATE MANIPULATORS
inline
int Resolver_DwarfReader::needBytes(bsl::size_t numBytes)
{
    IntPtr diff = d_endPtr - d_readPtr;
 
    if (diff < static_cast<IntPtr>(numBytes)) {
        BSLS_ASSERT(0 <= diff);
 
        return reload(numBytes);                                      // RETURN
    }
 
    return 0;
}
 
template <class TYPE>
int Resolver_DwarfReader::readLEB128(TYPE *dst)      // DWARF doc 7.6
{
    BSLMF_ASSERT(static_cast<TYPE>(-1) < 0);    // 'TYPE' must be signed
 
    int rc;
 
    Uint64 tmpDst = 0;
 
    unsigned char u = 0x80;
 
    enum { k_MAX_SHIFT = sizeof(*dst) * 8 };
 
    unsigned shift = -7;
    do {
        rc = readValue(&u);
        if (rc) {
            // Assign to '*dst' to silence the confused optimizer complaining
            // about 'maybe used before set' in caller.
 
            *dst = 0;
            return -1;                                                // RETURN
        }
 
        const Uint64 masked = 0x7f & u;
        shift += 7;
        tmpDst |= masked << shift;
    } while (0x80 & u);
 
    if (static_cast<TYPE>(-1) < 0) {
        // signed type, extend sign
 
        const Uint64 negFlag = static_cast<Uint64>(0x40) << shift;
        if (negFlag & tmpDst) {
            tmpDst |= ~(negFlag - 1);
        }
    }
 
    *dst = static_cast<TYPE>(tmpDst);
 
    return 0;
}
 
template <class TYPE>
int Resolver_DwarfReader::readULEB128(TYPE *dst)     // DWARF doc 7.6
{
    Uint64 tmpDst = 0;
 
    unsigned char u = 0x80;
 
    unsigned shift = 0;
    for (; (0x80 & u); shift += 7) {
        int rc = readValue(&u);
        if (0 != rc) {
            // Assign to '*dst' to silence the confused optimizer complaining
            // about 'maybe used before set' in caller.
 
            *dst = 0;
            return -1;                                                // RETURN
        }
 
        const Uint64 masked = 0x7f & u;
        tmpDst |= masked << shift;
    }
#if defined(BSLS_ASSERT_LEVEL_ASSERT_SAFE)
    if (shift >= sizeof(*dst) * 8 + 7) {
        // Assign to '*dst' to silence the confused optimizer complaining about
        // 'maybe used before set' in caller.
 
        *dst = 0;
        return -1;                                                    // RETURN
    }
#endif
 
    *dst = static_cast<TYPE>(tmpDst);
 
    return 0;
}
 
template <class TYPE>
inline
int Resolver_DwarfReader::readValue(TYPE *dst)
{
    int rc = needBytes(sizeof(*dst));
    if (rc) {
        // Assign to '*dst' to silence the confused optimizer complaining about
        // 'maybe used before set' in caller.
 
        *dst = 0;
        return -1;                                                    // RETURN
    }
 
    bsl::memcpy(dst, d_readPtr, sizeof(*dst));
    d_readPtr += sizeof(*dst);
 
    return 0;
}
 
inline
int Resolver_DwarfReader::skipBytes(Offset bytes)
{
    BSLS_ASSERT(bytes >= 0);
 
    if (bytes > d_endPtr - d_readPtr) {
        Offset off = offset();
 
        if (off         < d_beginOffset) {
            return -1;                                                // RETURN
        }
        if (off + bytes > d_endOffset) {
            return -1;                                                // RETURN
        }
 
        // By setting 'd_readPtr == d_endPtr' we guarantee that the next read
        // will trigger a reload.
 
        d_offset  += bytes + (d_readPtr - d_buffer_p);
        d_readPtr =  d_buffer_p;
        d_endPtr  =  d_readPtr;
    }
    else {
        d_readPtr += bytes;
    }
 
    return 0;
}
 
inline
int Resolver_DwarfReader::skipString()
{
    do {
        int rc = needBytes(1);
        if (rc) {
            return -1;                                                // RETURN
        }
    } while (*d_readPtr++);
 
    return 0;
}
 
// ACCESSORS
inline
int Resolver_DwarfReader::addressSize() const
{
    return d_addressSize;
}
 
inline
bool Resolver_DwarfReader::atEndOfSection() const
{
    return d_readPtr == d_endPtr &&
                              d_endOffset - d_offset == d_readPtr - d_buffer_p;
}
 
inline
Resolver_DwarfReader::Offset
Resolver_DwarfReader::offset() const
{
    return d_offset + (d_readPtr - d_buffer_p);
}
 
inline
Resolver_DwarfReader::Offset
Resolver_DwarfReader::offsetSize() const
{
    return d_offsetSize;
}
 
inline
bool Resolver_DwarfReader::isEnabled() const
{
    return 0 != d_buffer_p;
}
 
#endif
 
}  // close package namespace
 
 
#endif
 
// ----------------------------------------------------------------------------
// Copyright 2016 Bloomberg Finance L.P.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// ----------------------------- END-OF-FILE ----------------------------------
 
/** @} */
/** @} */
/** @} */