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performance: decoding deltas

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instead of converting to string with '0' and '1', do bitwise operations instead
This commit is contained in:
larshp 2017-05-20 12:04:18 +00:00
parent 44347b212d
commit 7586382eb1
1 changed files with 42 additions and 35 deletions
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77
src/zabapgit_git.prog.abap
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@ -685,82 +685,84 @@ CLASS lcl_git_pack IMPLEMENTATION.
DATA: lv_delta TYPE xstring,
lv_base TYPE xstring,
lv_result TYPE xstring,
lv_bitbyte TYPE ty_bitbyte,
* lv_bitbyte TYPE ty_bitbyte,
lv_offset TYPE i,
lv_message TYPE string,
lv_sha1 TYPE ty_sha1,
ls_object LIKE LINE OF ct_objects,
lv_len TYPE i,
lv_org TYPE x,
* lv_i TYPE i,
lv_x TYPE x.
FIELD-SYMBOLS: <ls_object> LIKE LINE OF ct_objects.
DEFINE _eat_byte.
lv_x = lv_delta(1).
lv_delta = lv_delta+1.
END-OF-DEFINITION.
lv_delta = is_object-data.
* find base
READ TABLE ct_objects ASSIGNING <ls_object> WITH KEY sha1 = is_object-sha1.
IF sy-subrc <> 0.
CONCATENATE 'Base not found,' is_object-sha1 INTO lv_message
SEPARATED BY space. "#EC NOTEXT
lcx_exception=>raise( lv_message ).
ELSE.
lv_base = <ls_object>-data.
ENDIF.
lcx_exception=>raise( |Base not found, { is_object-sha1 }| ).
ELSEIF <ls_object>-type = gc_type-ref_d.
* sanity check
IF <ls_object>-type = gc_type-ref_d.
lcx_exception=>raise( 'Delta, base eq delta' ).
ENDIF.
lv_base = <ls_object>-data.
* skip the 2 headers
delta_header( CHANGING cv_delta = lv_delta ).
delta_header( CHANGING cv_delta = lv_delta ).
CONSTANTS: lc_1 TYPE x VALUE '01',
lc_2 TYPE x VALUE '02',
lc_4 TYPE x VALUE '04',
lc_8 TYPE x VALUE '08',
lc_16 TYPE x VALUE '10',
lc_32 TYPE x VALUE '20',
lc_64 TYPE x VALUE '40',
lc_128 TYPE x VALUE '80'.
WHILE xstrlen( lv_delta ) > 0.
lv_x = lv_delta(1).
lv_delta = lv_delta+1.
lv_bitbyte = lcl_convert=>x_to_bitbyte( lv_x ).
_eat_byte.
lv_org = lv_x.
IF lv_bitbyte(1) = '1'. " MSB
IF lv_x BIT-AND lc_128 = lc_128. " MSB = 1
lv_offset = 0.
IF lv_bitbyte+7(1) = '1'.
lv_x = lv_delta(1).
lv_delta = lv_delta+1.
IF lv_org BIT-AND lc_1 = lc_1.
_eat_byte.
lv_offset = lv_x.
ENDIF.
IF lv_bitbyte+6(1) = '1'.
lv_x = lv_delta(1).
lv_delta = lv_delta+1.
IF lv_org BIT-AND lc_2 = lc_2.
_eat_byte.
lv_offset = lv_offset + lv_x * 256.
ENDIF.
IF lv_bitbyte+5(1) = '1'.
lv_x = lv_delta(1).
lv_delta = lv_delta+1.
IF lv_org BIT-AND lc_4 = lc_4.
_eat_byte.
lv_offset = lv_offset + lv_x * 65536.
ENDIF.
IF lv_bitbyte+4(1) = '1'.
lv_x = lv_delta(1).
lv_delta = lv_delta+1.
IF lv_org BIT-AND lc_8 = lc_8.
_eat_byte.
lv_offset = lv_offset + lv_x * 16777216. " hmm, overflow?
ENDIF.
lv_len = 0.
IF lv_bitbyte+3(1) = '1'.
lv_x = lv_delta(1).
lv_delta = lv_delta+1.
IF lv_org BIT-AND lc_16 = lc_16.
_eat_byte.
lv_len = lv_x.
ENDIF.
IF lv_bitbyte+2(1) = '1'.
lv_x = lv_delta(1).
lv_delta = lv_delta+1.
IF lv_org BIT-AND lc_32 = lc_32.
_eat_byte.
lv_len = lv_len + lv_x * 256.
ENDIF.
IF lv_bitbyte+1(1) = '1'.
lv_x = lv_delta(1).
lv_delta = lv_delta+1.
IF lv_org BIT-AND lc_64 = lc_64.
_eat_byte.
lv_len = lv_len + lv_x * 65536.
ENDIF.
@ -795,6 +797,11 @@ CLASS lcl_git_pack IMPLEMENTATION.
lt_deltas LIKE ct_objects.
lcl_progress=>show( iv_key = 'Decode'
iv_current = 1
iv_total = 1
iv_text = 'Deltas' ) ##NO_TEXT.
LOOP AT ct_objects INTO ls_object WHERE type = gc_type-ref_d.
DELETE ct_objects INDEX sy-tabix.
APPEND ls_object TO lt_deltas.