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### 2.15 Implementation details

#### 2.15.1 Internal functions

Description
These routines are used within BFD. They are not intended for export, but are documented here for completeness.

##### 2.15.1.1 `bfd_write_bigendian_4byte_int`

Synopsis

         bfd_boolean bfd_write_bigendian_4byte_int (bfd *, unsigned int);

Description
Write a 4 byte integer i to the output BFD abfd, in big endian order regardless of what else is going on. This is useful in archives.

##### 2.15.1.2 `bfd_put_size`

##### 2.15.1.3 `bfd_get_size`

Description
These macros as used for reading and writing raw data in sections; each access (except for bytes) is vectored through the target format of the BFD and mangled accordingly. The mangling performs any necessary endian translations and removes alignment restrictions. Note that types accepted and returned by these macros are identical so they can be swapped around in macros—for example, `libaout.h` defines `GET_WORD` to either `bfd_get_32` or `bfd_get_64`.

In the put routines, val must be a `bfd_vma`. If we are on a system without prototypes, the caller is responsible for making sure that is true, with a cast if necessary. We don't cast them in the macro definitions because that would prevent `lint` or `gcc -Wall` from detecting sins such as passing a pointer. To detect calling these with less than a `bfd_vma`, use `gcc -Wconversion` on a host with 64 bit `bfd_vma`'s.

         /* Byte swapping macros for user section data.  */

         #define bfd_put_8(abfd, val, ptr) \
           ((void) (*((unsigned char *) (ptr)) = (val) & 0xff))
         #define bfd_put_signed_8 \
           bfd_put_8
         #define bfd_get_8(abfd, ptr) \
           (*(const unsigned char *) (ptr) & 0xff)
         #define bfd_get_signed_8(abfd, ptr) \
           (((*(const unsigned char *) (ptr) & 0xff) ^ 0x80) - 0x80)

         #define bfd_put_16(abfd, val, ptr) \
           BFD_SEND (abfd, bfd_putx16, ((val),(ptr)))
         #define bfd_put_signed_16 \
           bfd_put_16
         #define bfd_get_16(abfd, ptr) \
           BFD_SEND (abfd, bfd_getx16, (ptr))
         #define bfd_get_signed_16(abfd, ptr) \
           BFD_SEND (abfd, bfd_getx_signed_16, (ptr))

         #define bfd_put_32(abfd, val, ptr) \
           BFD_SEND (abfd, bfd_putx32, ((val),(ptr)))
         #define bfd_put_signed_32 \
           bfd_put_32
         #define bfd_get_32(abfd, ptr) \
           BFD_SEND (abfd, bfd_getx32, (ptr))
         #define bfd_get_signed_32(abfd, ptr) \
           BFD_SEND (abfd, bfd_getx_signed_32, (ptr))

         #define bfd_put_64(abfd, val, ptr) \
           BFD_SEND (abfd, bfd_putx64, ((val), (ptr)))
         #define bfd_put_signed_64 \
           bfd_put_64
         #define bfd_get_64(abfd, ptr) \
           BFD_SEND (abfd, bfd_getx64, (ptr))
         #define bfd_get_signed_64(abfd, ptr) \
           BFD_SEND (abfd, bfd_getx_signed_64, (ptr))

         #define bfd_get(bits, abfd, ptr)                       \
           ((bits) == 8 ? (bfd_vma) bfd_get_8 (abfd, ptr)       \
            : (bits) == 16 ? bfd_get_16 (abfd, ptr)             \
            : (bits) == 32 ? bfd_get_32 (abfd, ptr)             \
            : (bits) == 64 ? bfd_get_64 (abfd, ptr)             \
            : (abort (), (bfd_vma) - 1))

         #define bfd_put(bits, abfd, val, ptr)                  \
           ((bits) == 8 ? bfd_put_8  (abfd, val, ptr)           \
            : (bits) == 16 ? bfd_put_16 (abfd, val, ptr)                \
            : (bits) == 32 ? bfd_put_32 (abfd, val, ptr)                \
            : (bits) == 64 ? bfd_put_64 (abfd, val, ptr)                \
            : (abort (), (void) 0))

##### 2.15.1.4 `bfd_h_put_size`

Description
These macros have the same function as their `bfd_get_x` brethren, except that they are used for removing information for the header records of object files. Believe it or not, some object files keep their header records in big endian order and their data in little endian order.

         /* Byte swapping macros for file header data.  */

         #define bfd_h_put_8(abfd, val, ptr) \
           bfd_put_8 (abfd, val, ptr)
         #define bfd_h_put_signed_8(abfd, val, ptr) \
           bfd_put_8 (abfd, val, ptr)
         #define bfd_h_get_8(abfd, ptr) \
           bfd_get_8 (abfd, ptr)
         #define bfd_h_get_signed_8(abfd, ptr) \
           bfd_get_signed_8 (abfd, ptr)

         #define bfd_h_put_16(abfd, val, ptr) \
           BFD_SEND (abfd, bfd_h_putx16, (val, ptr))
         #define bfd_h_put_signed_16 \
           bfd_h_put_16
         #define bfd_h_get_16(abfd, ptr) \
           BFD_SEND (abfd, bfd_h_getx16, (ptr))
         #define bfd_h_get_signed_16(abfd, ptr) \
           BFD_SEND (abfd, bfd_h_getx_signed_16, (ptr))

         #define bfd_h_put_32(abfd, val, ptr) \
           BFD_SEND (abfd, bfd_h_putx32, (val, ptr))
         #define bfd_h_put_signed_32 \
           bfd_h_put_32
         #define bfd_h_get_32(abfd, ptr) \
           BFD_SEND (abfd, bfd_h_getx32, (ptr))
         #define bfd_h_get_signed_32(abfd, ptr) \
           BFD_SEND (abfd, bfd_h_getx_signed_32, (ptr))

         #define bfd_h_put_64(abfd, val, ptr) \
           BFD_SEND (abfd, bfd_h_putx64, (val, ptr))
         #define bfd_h_put_signed_64 \
           bfd_h_put_64
         #define bfd_h_get_64(abfd, ptr) \
           BFD_SEND (abfd, bfd_h_getx64, (ptr))
         #define bfd_h_get_signed_64(abfd, ptr) \
           BFD_SEND (abfd, bfd_h_getx_signed_64, (ptr))

         /* Aliases for the above, which should eventually go away.  */

         #define H_PUT_64  bfd_h_put_64
         #define H_PUT_32  bfd_h_put_32
         #define H_PUT_16  bfd_h_put_16
         #define H_PUT_8   bfd_h_put_8
         #define H_PUT_S64 bfd_h_put_signed_64
         #define H_PUT_S32 bfd_h_put_signed_32
         #define H_PUT_S16 bfd_h_put_signed_16
         #define H_PUT_S8  bfd_h_put_signed_8
         #define H_GET_64  bfd_h_get_64
         #define H_GET_32  bfd_h_get_32
         #define H_GET_16  bfd_h_get_16
         #define H_GET_8   bfd_h_get_8
         #define H_GET_S64 bfd_h_get_signed_64
         #define H_GET_S32 bfd_h_get_signed_32
         #define H_GET_S16 bfd_h_get_signed_16
         #define H_GET_S8  bfd_h_get_signed_8

##### 2.15.1.5 `bfd_log2`

Synopsis

         unsigned int bfd_log2 (bfd_vma x);

Description
Return the log base 2 of the value supplied, rounded up. E.g., an x of 1025 returns 11. A x of 0 returns 0.