The source code is as follows:
* &---------------------------------------------- --------------------------*
* & Report ZBLOCKCHAIN
* &------------------------------------------------- -----------------------*
* &
* &------------------------------------------------- -----------------------*
REPORT zblockchain.
PARAMETERS: diffle TYPE char5 default '00000',
noblock TYPE i DEFAULT 2.
DATA:blockdata TYPE zcl_abap_blockchain_tool=>tt_block .
DATA:blockdataline LIKE LINE OF blockdata,
timestamp TYPE timestamp,
combineddata TYPE string,
prevblockdata LIKE LINE OF blockdata,
nonce TYPE i VALUE 1,
noncestring TYPE string,
flag TYPE c,
difflength TYPE i,
gethash TYPE REF TO cl_abap_message_digest.
blockdataline-index = 0.
blockdataline-data = 'Jerry first Genesis block'.
blockdataline-phash = '000000'.
GET TIME STAMP FIELD timestamp.
blockdataline-timestamp = timestamp.
blockdataline-nonce = 0.
CONCATENATE blockdataline-index blockdataline-data blockdataline-phash blockdataline-timestamp blockdataline-nonce INTO combineddata.
CALL METHOD cl_abap_message_digest=>calculate_hash_for_char
EXPORTING
if_algorithm = 'SHA1'
if_data = combineddata
IMPORTING
ef_hashstring = blockdataline-chash.
APPEND blockdataline TO blockdata.
noblock = noblock - 1.
difflength = strlen(diffle).
DO noblock TIMES.
blockdataline-index = sy-tabix.
CONCATENATE `Jerry's Block ` blockdataline-index INTO blockdataline-data SEPARATED BY '-'.
READ TABLE blockdata INTO prevblockdata INDEX blockdataline-index.
IF sy-subrc EQ 0.
blockdataline-phash = prevblockdata-chash.
ENDIF.
GET TIME STAMP FIELD timestamp.
blockdataline-timestamp = timestamp.
WHILE flag EQ abap_false.
noncestring = nonce.
CONCATENATE blockdataline-index blockdataline-data blockdataline-phash blockdataline-timestamp noncestring INTO combineddata.
CALL METHOD cl_abap_message_digest=>calculate_hash_for_char
EXPORTING
if_algorithm = 'SHA1'
if_data = combineddata
IMPORTING
ef_hashstring = blockdataline-chash.
IF blockdataline-chash(difflength) = diffle.
flag = 'X'.
blockdataline-nonce = nonce.
APPEND blockdataline TO blockdata.
nonce = 1.
CLEAR:blockdataline.
ENDIF.
nonce = nonce + 1.
ENDWHILE.
CLEAR flag.
ENDDO.
DATA: g_alv_tree TYPE REF TO cl_gui_alv_tree,
gt_data TYPE STANDARD TABLE OF zcl_abap_blockchain_tool=>ty_displayed_node,
ok_code LIKE sy-ucomm,
save_ok LIKE sy-ucomm,
ls_data LIKE LINE OF gt_data.
FIELD-SYMBOLS: <field> TYPE LINE OF LVC_T_FCAT.
DATA(lo_tool) = NEW zcl_abap_blockchain_tool( blockdata ).
DATA(lt_fieldcat) = lo_tool->get_fieldcat_by_data(ls_data).
PERFORM change_label.
CALL SCREEN 100.
DEFINE define_label.
READ TABLE lt_fieldcat ASSIGNING <field> INDEX &1.
<field>-seltext = <field>-reptext = <field>-scrtext_m = <field>-scrtext_s = <field>-scrtext_l = & amp;2.
<field>-outputlen = & amp;3.
END-OF-DEFINITION.
FORM change_label.
define_label 1 'Block Data' 20.
define_label 2 'Hash' 40.
define_label 3 'Nonce' 10.
define_label 4 'Timestamp' 20.
ENDFORM.
FORM init_tree.
g_alv_tree = lo_tool->get_tree( ).
DATA l_hierarchy_header TYPE treev_hhdr.
PERFORM build_hierarchy_header CHANGING l_hierarchy_header.
CALL METHOD g_alv_tree->set_table_for_first_display
EXPORTING
is_hierarchy_header = l_hierarchy_header
CHANGING
it_fieldcatalog = lt_fieldcat
it_outtab = gt_data.
PERFORM create_tree.
g_alv_tree->frontend_update( ).
lo_tool->expand( ).
ENDFORM.
FORM create_tree.
lo_tool->render_tree( ).
ENDFORM.
FORM build_hierarchy_header CHANGING p_hierarchy_header TYPE treev_hhdr.
p_hierarchy_header-heading = 'BlockChain list'.
p_hierarchy_header-width = 30.
p_hierarchy_header-width_pix = ' '.
ENDFORM.
FORM exit_program.
LEAVE PROGRAM.
ENDFORM.
MODULE pbo OUTPUT.
SET PF-STATUS 'MAIN100'.
SET TITLEBAR 'MAINTITLE'.
IF g_alv_tree IS INITIAL.
PERFORM init_tree.
CALL METHOD cl_gui_cfw=>flush
EXCEPTIONS
cntl_system_error = 1
cntl_error = 2.
ASSERT sy-subrc = 0.
ENDIF.
ENDMODULE.
MODULE pai INPUT.
save_ok = ok_code.
CLEAR ok_code.
CASE save_ok.
WHEN 'EXIT' OR 'BACK' OR 'CANC'.
PERFORM exit_program.
WHEN OTHERS.
CALL METHOD cl_gui_cfw=>dispatch.
ENDCASE.
CALL METHOD cl_gui_cfw=>flush.
ENDMODULE.
The code is explained below:
First, it defines a report ZBLOCKCHAIN that has two parameters diffle and noblock. diffle is a five-character string that defines the difficulty of the blockchain, while noblock is an integer that defines the number of blocks in the blockchain .
Then, it defines some data objects, including blockdata, which is a table used to store blocks in the blockchain; blockdataline, which represents a block, Contains the block index, data, hash value of the previous block, timestamp and random number; timestamp is a timestamp; combineddata is a string, Used to store block information and used to generate hash values; prevblockdata is used to store information of the previous block; nonce is a random number used to generate hash values Hash value; noncestring is the string representation of nonce; flag is a flag used to control loops; difflength is the length of diffle; gethash is an object reference used to generate hash values.
Next, it creates the genesis block, the first block of the blockchain. The index of the genesis block is 0, the data is Jerry first Genesis block, the hash value of the previous block is 000000, the timestamp is the current time, and the random number is 0. It then concatenates the information into a string, then calls the cl_abap_message_digest=>calculate_hash_for_char method to generate a hash value and stores the hash value in blockdataline-chash. Finally, it adds blockdataline to blockdata.
Then, it creates the remaining blocks. This is achieved through a loop, the number of loops is noblock - 1. In each loop, it first sets the index and data of the block, then reads the information of the previous block, sets its hash value to the current block’s phash, and sets the current block timestamp, and then in an inner loop, generate random numbers, concatenate the block information, and generate a hash value. If the first difflength characters of the hash value and diffle are equal, then exit the inner loop and add the current block to blockdata, otherwise, add a random number and continue the inner loop.