{"id":22,"date":"2015-09-01T14:48:25","date_gmt":"2015-09-01T14:48:25","guid":{"rendered":"http:\/\/coolt.ch\/notizen\/?p=22"},"modified":"2015-09-08T06:14:27","modified_gmt":"2015-09-08T06:14:27","slug":"bytes-einlesen","status":"publish","type":"post","link":"https:\/\/coolt.ch\/notizen\/bytes-einlesen\/","title":{"rendered":"Bytes einlesen"},"content":{"rendered":"

Byte-Struktur
\n<\/strong>– Formatvariablen definieren definieren Datenstruktur
\n– Formatvariablen stehen in einem String
\n– f\u00fcr jede Formatvariable muss eine Variable mitgegeben werden
\n– folgen grosse Datenpakete als, muss deren L\u00e4nge
\n.\u00a0 bekannt sein und wird vor der Stringvariable eingef\u00fcgt
\n– “ > “ bedeutet big endian,\u00a0 “ < “ littel endian<\/p>\n

command = pack(‚ >BH‘ + str(length) + ’s ‚, typ, command, length, data)<\/p>\n

\"Python_Struct_BefehlsTabelle\"<\/a><\/p>\n

Vor Daten Schl\u00fcsselw\u00f6rter einf\u00fcgen<\/strong>
\ndata = pack(‚ >BBH’+str(length)+’s ‚, testnumber, time, command, length, data)<\/p>\n

Schl\u00fcsselw\u00f6rter vor Data extrahieren<\/strong>
\ntestnumber = unpack(‚>B‘, data[0:1])
\ntime = unpack(‚>B‘, data[1:2])<\/p>\n

Daten ohne Schl\u00fcsselw\u00f6rter
\n<\/strong>data[:4]\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 die ersten 4 Bytes werden weggelassen<\/p>\n

Big Endian \/ Littel Endian<\/strong>
\nbig endian = normal \u00a0\u00a0\u00a0\u00a0 a = (‚>B‘, 3) \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 output\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 a = 00 03
\nlittle endian\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 a = (‚<B‘, 3) \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 output\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 a = 03 00<\/p>\n

Info
\n<\/strong>In Python werden Daten als String \u00fcbergeben. Sollen diese eine bestimmte Byte-Struktur haben, helfen die Funktionen pack() and unpack().
\nimport struct *<\/p>\n","protected":false},"excerpt":{"rendered":"

Byte-Struktur – Formatvariablen definieren definieren Datenstruktur – Formatvariablen stehen in einem String – f\u00fcr jede Formatvariable muss eine Variable mitgegeben werden – folgen grosse Datenpakete als, muss deren L\u00e4nge .\u00a0 bekannt sein und wird vor der Stringvariable eingef\u00fcgt – “ > “ bedeutet big endian,\u00a0 “ < “ littel endian command = pack(‚ >BH‘ + … Bytes einlesen<\/span> weiterlesen<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[2],"tags":[6,10],"_links":{"self":[{"href":"https:\/\/coolt.ch\/notizen\/wp-json\/wp\/v2\/posts\/22"}],"collection":[{"href":"https:\/\/coolt.ch\/notizen\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/coolt.ch\/notizen\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/coolt.ch\/notizen\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/coolt.ch\/notizen\/wp-json\/wp\/v2\/comments?post=22"}],"version-history":[{"count":4,"href":"https:\/\/coolt.ch\/notizen\/wp-json\/wp\/v2\/posts\/22\/revisions"}],"predecessor-version":[{"id":51,"href":"https:\/\/coolt.ch\/notizen\/wp-json\/wp\/v2\/posts\/22\/revisions\/51"}],"wp:attachment":[{"href":"https:\/\/coolt.ch\/notizen\/wp-json\/wp\/v2\/media?parent=22"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/coolt.ch\/notizen\/wp-json\/wp\/v2\/categories?post=22"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/coolt.ch\/notizen\/wp-json\/wp\/v2\/tags?post=22"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}